0001212545FALSE00012125452025-07-312025-07-310001212545us-gaap:CommonStockMember2025-07-312025-07-310001212545us-gaap:NoncumulativePreferredStockMember2025-07-312025-07-31

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 8-K

CURRENT REPORT
Pursuant to Section 13 or 15(d) of the
Securities Exchange Act of 1934

Date of Report (Date of earliest event reported):  July 31, 2025


WESTERN ALLIANCE BANCORPORATION
(Exact name of registrant as specified in its charter)

Delaware001-3255088-0365922
(State or other jurisdiction
of incorporation)
(Commission
File Number)
(IRS Employer
Identification No.)

One E. Washington Street, Phoenix, Arizona  85004
 (Address of principal executive offices)               (Zip Code)

(602) 389-3500
(Registrant's telephone number, including area code)

Not Applicable
(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:
Title of each classTrading Symbol(s)Name of each exchange on which registered
Common Stock, $0.0001 Par ValueWALNew York Stock Exchange
Depositary Shares, Each Representing a 1/400th Interest in a Share of
4.250% Fixed-Rate Reset Non-Cumulative Perpetual Preferred Stock, Series A
WAL PrANew York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).
Emerging growth company

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨





ITEM 8.01. OTHER EVENTS.
Quarterly Common and Preferred Stock Dividend.
At the meeting of the Board of Directors (the “Board”) of Western Alliance Bancorporation held on July 31, 2025, the Board declared a quarterly cash dividend of $0.38 per share of common stock. The dividend will be payable on August 29, 2025 to shareholders of record as of August 14, 2025.
The Board also declared a quarterly cash dividend of $106.25 per share (equivalent to $0.265625 per depositary share) on its 4.250% Fixed Rate Reset Non-Cumulative Perpetual Preferred Stock, Series A. The dividend will be payable on September 30, 2025 to shareholders of record as of September 15, 2025.
ITEM 9.01. FINANCIAL STATEMENTS AND EXHIBITS.
(d) Exhibits.
104 Cover Page Interactive Data File (embedded within the Inline XBRL document)




SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.
 WESTERN ALLIANCE BANCORPORATION
(Registrant)
 
 
/s/ Dale Gibbons
Dale Gibbons
Vice Chairman and
Chief Financial Officer
 
 
 
Date:July 31, 2025


v3.25.2
DEI Document
Jul. 31, 2025
Entity Information [Line Items]  
Entity Central Index Key 0001212545
Amendment Flag false
Document Type 8-K
Document Period End Date Jul. 31, 2025
Entity Incorporation, State or Country Code DE
Entity File Number 001-32550
Written Communications false
Soliciting Material false
Pre-commencement Tender Offer false
Pre-commencement Issuer Tender Offer false
Entity Emerging Growth Company false
Entity Tax Identification Number 88-0365922
Entity Registrant Name WESTERN ALLIANCE BANCORPORATION
Entity Address, Address Line One One E. Washington Street
Entity Address, City or Town Phoenix
Entity Address, State or Province AZ
Entity Address, Postal Zip Code 85004
City Area Code 602
Local Phone Number 389-3500
Common Stock [Member]  
Entity Information [Line Items]  
Title of 12(b) Security Common Stock, $0.0001 Par Value
Trading Symbol WAL
Security Exchange Name NYSE
Noncumulative Preferred Stock  
Entity Information [Line Items]  
Title of 12(b) Security Depositary Shares, Each Representing a 1/400th Interest in a Share of 4.250% Fixed-Rate Reset Non-Cumulative Perpetual Preferred Stock, Series A
Trading Symbol WAL PrA
Security Exchange Name NYSE

{
 "version": "2.2",
 "instance": {
  "wal-20250731.htm": {
   "nsprefix": "wal",
   "nsuri": "http://www.westernalliancebancorp.com/20250731",
   "dts": {
    "inline": {
     "local": [
      "wal-20250731.htm"
     ]
    },
    "schema": {
     "local": [
      "wal-20250731.xsd"
     ],
     "remote": [
      "http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xl-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xlink-2003-12-31.xsd",
      "http://www.xbrl.org/2005/xbrldt-2005.xsd",
      "http://www.xbrl.org/2006/ref-2006-02-27.xsd",
      "http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd",
      "http://www.xbrl.org/lrr/role/net-2009-12-16.xsd",
      "https://www.xbrl.org/2020/extensible-enumerations-2.0.xsd",
      "https://www.xbrl.org/dtr/type/2020-01-21/types.xsd",
      "https://www.xbrl.org/dtr/type/2024-01-31/types.xsd",
      "https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd",
      "https://xbrl.fasb.org/srt/2025/elts/srt-roles-2025.xsd",
      "https://xbrl.fasb.org/srt/2025/elts/srt-types-2025.xsd",
      "https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd",
      "https://xbrl.fasb.org/us-gaap/2025/elts/us-roles-2025.xsd",
      "https://xbrl.fasb.org/us-gaap/2025/elts/us-types-2025.xsd",
      "https://xbrl.sec.gov/country/2025/country-2025.xsd",
      "https://xbrl.sec.gov/dei/2025/dei-2025.xsd",
      "https://xbrl.sec.gov/stpr/2025/stpr-2025.xsd"
     ]
    },
    "definitionLink": {
     "local": [
      "wal-20250731_def.xml"
     ]
    },
    "labelLink": {
     "local": [
      "wal-20250731_lab.xml"
     ]
    },
    "presentationLink": {
     "local": [
      "wal-20250731_pre.xml"
     ]
    }
   },
   "keyStandard": 22,
   "keyCustom": 0,
   "axisStandard": 1,
   "axisCustom": 0,
   "memberStandard": 2,
   "memberCustom": 0,
   "hidden": {
    "total": 2,
    "http://xbrl.sec.gov/dei/2025": 2
   },
   "contextCount": 3,
   "entityCount": 1,
   "segmentCount": 2,
   "elementCount": 31,
   "unitCount": 0,
   "baseTaxonomies": {
    "http://xbrl.sec.gov/dei/2025": 25
   },
   "report": {
    "R1": {
     "role": "http://www.westernalliancebancorp.com/role/DEIDocument",
     "longName": "0000001 - Document - DEI Document",
     "shortName": "DEI Document",
     "isDefault": "true",
     "groupType": "document",
     "subGroupType": "",
     "menuCat": "Cover",
     "order": "1",
     "firstAnchor": {
      "contextRef": "c-1",
      "name": "dei:DocumentType",
      "unitRef": null,
      "xsiNil": "false",
      "lang": "en-US",
      "decimals": null,
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "reportCount": 1,
      "baseRef": "wal-20250731.htm",
      "first": true,
      "unique": true
     },
     "uniqueAnchor": {
      "contextRef": "c-1",
      "name": "dei:DocumentType",
      "unitRef": null,
      "xsiNil": "false",
      "lang": "en-US",
      "decimals": null,
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "reportCount": 1,
      "baseRef": "wal-20250731.htm",
      "first": true,
      "unique": true
     }
    }
   },
   "tag": {
    "dei_AmendmentFlag": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "AmendmentFlag",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Amendment Flag",
        "label": "Amendment Flag",
        "documentation": "Boolean flag that is true when the XBRL content amends previously-filed or accepted submission."
       }
      }
     },
     "auth_ref": []
    },
    "dei_CityAreaCode": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "CityAreaCode",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "City Area Code",
        "label": "City Area Code",
        "documentation": "Area code of city"
       }
      }
     },
     "auth_ref": []
    },
    "us-gaap_ClassOfStockDomain": {
     "xbrltype": "domainItemType",
     "nsuri": "http://fasb.org/us-gaap/2025",
     "localname": "ClassOfStockDomain",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Class of Stock [Domain]",
        "label": "Class of Stock [Domain]"
       }
      }
     },
     "auth_ref": []
    },
    "us-gaap_CommonStockMember": {
     "xbrltype": "domainItemType",
     "nsuri": "http://fasb.org/us-gaap/2025",
     "localname": "CommonStockMember",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Common Stock [Member]",
        "label": "Common Stock [Member]"
       }
      }
     },
     "auth_ref": []
    },
    "wal_DocumentInformationAbstract": {
     "xbrltype": "stringItemType",
     "nsuri": "http://www.westernalliancebancorp.com/20250731",
     "localname": "DocumentInformationAbstract",
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Document Information [Abstract]",
        "label": "Document Information [Abstract]",
        "documentation": "Document Information [Abstract]"
       }
      }
     },
     "auth_ref": []
    },
    "dei_DocumentPeriodEndDate": {
     "xbrltype": "dateItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "DocumentPeriodEndDate",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Document Period End Date",
        "label": "Document Period End Date",
        "documentation": "For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period. The format of the date is YYYY-MM-DD."
       }
      }
     },
     "auth_ref": []
    },
    "dei_DocumentType": {
     "xbrltype": "submissionTypeItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "DocumentType",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Document Type",
        "label": "Document Type",
        "documentation": "The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'."
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntitiesTable": {
     "xbrltype": "stringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntitiesTable",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entities [Table]",
        "label": "Entities [Table]",
        "documentation": "Container to assemble all relevant information about each entity associated with the document instance"
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityAddressAddressLine1": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityAddressAddressLine1",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Address, Address Line One",
        "label": "Entity Address, Address Line One",
        "documentation": "Address Line 1 such as Attn, Building Name, Street Name"
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityAddressCityOrTown": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityAddressCityOrTown",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Address, City or Town",
        "label": "Entity Address, City or Town",
        "documentation": "Name of the City or Town"
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityAddressPostalZipCode": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityAddressPostalZipCode",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Address, Postal Zip Code",
        "label": "Entity Address, Postal Zip Code",
        "documentation": "Code for the postal or zip code"
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityAddressStateOrProvince": {
     "xbrltype": "stateOrProvinceItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityAddressStateOrProvince",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Address, State or Province",
        "label": "Entity Address, State or Province",
        "documentation": "Name of the state or province."
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityCentralIndexKey": {
     "xbrltype": "centralIndexKeyItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityCentralIndexKey",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Central Index Key",
        "label": "Entity Central Index Key",
        "documentation": "A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK."
       }
      }
     },
     "auth_ref": [
      "r1"
     ]
    },
    "dei_EntityDomain": {
     "xbrltype": "domainItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityDomain",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity [Domain]",
        "label": "Entity [Domain]",
        "documentation": "All the names of the entities being reported upon in a document. Any legal structure used to conduct activities or to hold assets. Some examples of such structures are corporations, partnerships, limited liability companies, grantor trusts, and other trusts. This item does not include business and geographical segments which are included in the geographical or business segments domains."
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityEmergingGrowthCompany": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityEmergingGrowthCompany",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Emerging Growth Company",
        "label": "Entity Emerging Growth Company",
        "documentation": "Indicate if registrant meets the emerging growth company criteria."
       }
      }
     },
     "auth_ref": [
      "r1"
     ]
    },
    "dei_EntityFileNumber": {
     "xbrltype": "fileNumberItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityFileNumber",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity File Number",
        "label": "Entity File Number",
        "documentation": "Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen."
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityIncorporationStateCountryCode": {
     "xbrltype": "edgarStateCountryItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityIncorporationStateCountryCode",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Incorporation, State or Country Code",
        "label": "Entity Incorporation, State or Country Code",
        "documentation": "Two-character EDGAR code representing the state or country of incorporation."
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityInformationLineItems": {
     "xbrltype": "stringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityInformationLineItems",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Information [Line Items]",
        "label": "Entity Information [Line Items]",
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table."
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityRegistrantName": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityRegistrantName",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Registrant Name",
        "label": "Entity Registrant Name",
        "documentation": "The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC."
       }
      }
     },
     "auth_ref": [
      "r1"
     ]
    },
    "dei_EntityTaxIdentificationNumber": {
     "xbrltype": "employerIdItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityTaxIdentificationNumber",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Tax Identification Number",
        "label": "Entity Tax Identification Number",
        "documentation": "The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS."
       }
      }
     },
     "auth_ref": [
      "r1"
     ]
    },
    "dei_LegalEntityAxis": {
     "xbrltype": "stringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "LegalEntityAxis",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Legal Entity [Axis]",
        "label": "Legal Entity [Axis]",
        "documentation": "The set of legal entities associated with a report."
       }
      }
     },
     "auth_ref": []
    },
    "dei_LocalPhoneNumber": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "LocalPhoneNumber",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Local Phone Number",
        "label": "Local Phone Number",
        "documentation": "Local phone number for entity."
       }
      }
     },
     "auth_ref": []
    },
    "us-gaap_NoncumulativePreferredStockMember": {
     "xbrltype": "domainItemType",
     "nsuri": "http://fasb.org/us-gaap/2025",
     "localname": "NoncumulativePreferredStockMember",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Noncumulative Preferred Stock",
        "label": "Noncumulative Preferred Stock [Member]"
       }
      }
     },
     "auth_ref": []
    },
    "dei_PreCommencementIssuerTenderOffer": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "PreCommencementIssuerTenderOffer",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Pre-commencement Issuer Tender Offer",
        "label": "Pre-commencement Issuer Tender Offer",
        "documentation": "Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act."
       }
      }
     },
     "auth_ref": [
      "r3"
     ]
    },
    "dei_PreCommencementTenderOffer": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "PreCommencementTenderOffer",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Pre-commencement Tender Offer",
        "label": "Pre-commencement Tender Offer",
        "documentation": "Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act."
       }
      }
     },
     "auth_ref": [
      "r5"
     ]
    },
    "dei_Security12bTitle": {
     "xbrltype": "securityTitleItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "Security12bTitle",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Title of 12(b) Security",
        "label": "Title of 12(b) Security",
        "documentation": "Title of a 12(b) registered security."
       }
      }
     },
     "auth_ref": [
      "r0"
     ]
    },
    "dei_SecurityExchangeName": {
     "xbrltype": "edgarExchangeCodeItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "SecurityExchangeName",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Security Exchange Name",
        "label": "Security Exchange Name",
        "documentation": "Name of the Exchange on which a security is registered."
       }
      }
     },
     "auth_ref": [
      "r2"
     ]
    },
    "dei_SolicitingMaterial": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "SolicitingMaterial",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Soliciting Material",
        "label": "Soliciting Material",
        "documentation": "Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as soliciting material pursuant to Rule 14a-12 under the Exchange Act."
       }
      }
     },
     "auth_ref": [
      "r4"
     ]
    },
    "us-gaap_StatementClassOfStockAxis": {
     "xbrltype": "stringItemType",
     "nsuri": "http://fasb.org/us-gaap/2025",
     "localname": "StatementClassOfStockAxis",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Class of Stock [Axis]",
        "label": "Class of Stock [Axis]"
       }
      }
     },
     "auth_ref": []
    },
    "dei_TradingSymbol": {
     "xbrltype": "tradingSymbolItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "TradingSymbol",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Trading Symbol",
        "label": "Trading Symbol",
        "documentation": "Trading symbol of an instrument as listed on an exchange."
       }
      }
     },
     "auth_ref": []
    },
    "dei_WrittenCommunications": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "WrittenCommunications",
     "presentation": [
      "http://www.westernalliancebancorp.com/role/DEIDocument"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Written Communications",
        "label": "Written Communications",
        "documentation": "Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as written communications pursuant to Rule 425 under the Securities Act."
       }
      }
     },
     "auth_ref": [
      "r6"
     ]
    }
   }
  }
 },
 "std_ref": {
  "r0": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "12",
   "Subsection": "b"
  },
  "r1": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "12",
   "Subsection": "b-2"
  },
  "r2": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "12",
   "Subsection": "d1-1"
  },
  "r3": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "13e",
   "Subsection": "4c"
  },
  "r4": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "14a",
   "Subsection": "12"
  },
  "r5": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "14d",
   "Subsection": "2b"
  },
  "r6": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Securities Act",
   "Number": "230",
   "Section": "425"
  }
 }
}