Business Combinations and Asset Acquisitions - Pro Forma (Details) - Umpqua Bank and Columbia Banking System Merger - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Asset Acquisition [Line Items]
Business acquisition, pro forma net interest income	$ 1,494,339	$ 1,498,444
Business Acquisition, Pro Forma Non-interest Income	172,231	232,658
Business Acquisition, Pro Forma Net Income (Loss)	530,049	$ 363,786
Business Combination, Acquisition Related Costs - Combined for proforma	$ 192,500