Acquisitions - Schedule of Recognized Identifiable Assets Acquired and Liabilities Assumed (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Feb. 01, 2022 USD ($) office $ / shares shares	Dec. 31, 2022 USD ($) segment	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Business Acquisition [Line Items]
Goodwill		$ 1,100,900	$ 621,600	$ 621,600
Estimated useful lives of related deposits		12 years
Number of operating segments | segment		1
Great Western Bank
Business Acquisition [Line Items]
Number of banking offices | office	174
Cash and cash equivalents	$ 2,006,900
Business Combination, Recognized Identifiable Assets Acquirede and Liablilities Assumed, Current Assets, Securities Purchased Under Agreement to Resell	101,100
business combinatios, recognized identifiable assets acquired and liabilities assumed, loans held	217,000
Investment securities	2,699,000
Business Combinations, Recognized Identifiable Assets Acquired And Liabilities Assumed, Loans Held for Investment	7,705,000
Business Combinations, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loans and Leases Receivable, Allowance	(59,500)
Premises and equipment	144,700
Business Combinations, Recognized Identifiable Assests Acquired and Liabilities Assumed Other Real Estate Owned	15,800
Company owned life insurance	186,600
Core deposit intangible assets	50,100
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	22,800
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Mortgage Servicing Rights	1,300
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets	60,200
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Other Assets	200,800
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed, Accounts Payable And Accrued Expense	110,400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Federal Home Loan Bank Advances	122,900
Total assets acquired	13,351,800
Deposits	11,688,000
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed, Other Liabilities	36,400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities	76,100
Total liabilities assumed	12,107,800
Net assets acquired	1,244,000
Class A common stock	1,723,300
Total consideration paid	1,723,300
Goodwill	479,300
Buisness Combination, Recognizable Assets Acquired and Liabilities Assumed, Securities Sold Under Repurchase Agreement	74,000
Business Combination, Consideration Paid in Lieu of Fractional Shares	$ 13
Great Western Bank | Class A Common Stock
Business Acquisition [Line Items]
Common stock issued (in shares) | shares	46,879,601
Business Acquisition, Share Price | $ / shares	$ 36.76
Core Deposits Intangibles
Business Acquisition [Line Items]
Estimated useful lives of related deposits	10 years	10 years