Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Feb. 28, 2023
Income Tax Contingency [Line Items]
Deferred Tax Assets, Net	$ 469,800		$ 469,800
Provision for income taxes	48,127	$ 27,473	$ 88,944	$ 84,362
Effective Tax Rate as a Percentage of pre-tax Income (loss)			25.80%	24.90%
Umpqua Bank and Columbia Banking System Merger
Income Tax Contingency [Line Items]
Deferred Tax Assets, Net					$ 254,900
State and Local Jurisdiction
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	$ 2,500		$ 2,500