CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
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| Statement of Comprehensive Income [Abstract] | ||
| Net income | $ 189.2 | $ 199.1 |
| Other comprehensive income (loss), net: | ||
| Unrealized (loss) gain on AFS securities, net of tax effect of $25.1 and $(19.4), respectively | (74.2) | 55.7 |
| Unrealized loss on SERP, net of tax effect of $0.1 and $—, respectively | (0.3) | 0.0 |
| Unrealized gain on junior subordinated debt, net of tax effect of $(0.3) and $(0.4), respectively | 1.0 | 1.1 |
| Reclassification adjustment for gain on sale of AFS securities included in income, net of tax effect of $12.7 and $0.5, respectively | (37.8) | (1.6) |
| Net other comprehensive (loss) income | (111.3) | 55.2 |
| Comprehensive income attributable to noncontrolling interest | 7.1 | 0.0 |
| Comprehensive income attributable to Western Alliance | $ 70.8 | $ 254.3 |
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- Definition Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount, after tax, before reclassification adjustment, of unrealized gain (loss) from increase (decrease) in instrument-specific credit risk of financial liability measured under fair value option. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount after tax and reclassification adjustments of other comprehensive income (loss). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- References No definition available.
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| X | ||||||||||
- Definition Amount after tax of other comprehensive income (loss) attributable to noncontrolling interests. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount, after tax and reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount, after tax and before adjustment, of unrealized holding gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Excludes unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- References No definition available.
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