Business Combinations and Asset Acquisitions - Assets acquired and liabilities assumed (Details) - USD ($)	Feb. 28, 2023	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Asset Acquisition [Line Items]
Goodwill		$ 1,030,142,000	$ 0
Umpqua Bank and Columbia Banking System Merger
Asset Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 2,337,632,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	274,587,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loans held for Sale	2,358,000
Business Combination, Acquired Receivable, Fair Value	10,884,106,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Restricted Equity Securities	101,760,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	203,270,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	710,230,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets	253,481,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Assets	571,753,000
Assets acquired	19,226,816,000	19,226,816,000		$ 0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits	15,193,474,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits - Securities Sold Under Agreements to Repurcahse	70,025,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits, Borrowings	2,294,360,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits - Junior and Other Subordinated Debentures	20,310,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Liabilities	341,157,000
Liabilities assumed	17,919,326,000	17,919,326,000		0
Net assets acquired	1,307,490,000	$ 1,307,490,000		$ 0
Goodwill	1,030,142,000
Umpqua Bank and Columbia Banking System Merger | Securities Investment
Asset Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities	$ 6,225,271,000