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Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Aug. 31, 2025	Dec. 31, 2024
Income Tax Contingency [Line Items]
Deferred Tax Assets, Net	$ 392		$ 392
Income Tax Expense (Benefit)	23	$ 50	$ 111	$ 136
Effective Tax Rate as a Percentage of pre-tax Income (loss)			24.90%	25.80%
Affordable housing tax credit investments	328		$ 328			$ 221
Unfunded affordable housing tax credit commitments	143		143			$ 95
Columbia Banking Systems and Pacific Premier Bancorp Merger
Income Tax Contingency [Line Items]
Deferred Tax Assets, Net					$ 94
Affordable housing tax credit investments					75
Unfunded affordable housing tax credit commitments					$ 29
State and Local Jurisdiction
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	5		5
State and Local Jurisdiction | Columbia Banking Systems and Pacific Premier Bancorp Merger
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	$ 3		$ 3

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