Loans Held for Investment - Schedule of Allowance for Credit Losses for Loans Held for Investment (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($) Investments	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) Investments	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) Investments
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 226,100,000	$ 247,200,000	$ 220,100,000	$ 122,300,000
Provision charged to operating expense	11,700,000	(1,700,000)	26,900,000	59,600,000
Loans Charged-Off(2)	(14,100,000)	(3,700,000)	(23,000,000.0)	(23,600,000)
Ending balance	224,600,000	220,400,000	224,600,000	220,400,000
Provisional ACL Recorded for PCD loans		(24,800,000)		59,500,000
Off-Balance Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal)	9,900,000	(1,700,000)	22,100,000	55,600,000
Financing Receivable, Allowance for Credit Loss, Recovery	2,700,000	3,400,000	5,400,000	6,600,000
Interest Receivable	119,100,000		119,100,000		$ 118,300,000
Debt Securities, Available-for-sale, Realized Loss	$ 0	0	$ (23,500,000)	0
Allowance for Credit Losses					$ 0
Investment securities in an unrealized loss position (securities) | Investments	1,030		1,030		1,222
Debt Securities, Available-for-sale, Realized Gain	$ 0	0		0
Securities Sold under Agreements to Repurchase, Fair Value of Collateral	7,227,800,000		$ 7,227,800,000		$ 4,998,900,000
Securities Loaned or Sold under Agreements to Repurchase, Fair Value Disclosure	6,455,100,000		6,455,100,000		4,432,000,000
Callable Within One Year
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Amortized cost of investment securities callable after one year but within five years	1,593,800,000		1,593,800,000
Fair value of investment securities callable after one year but within five years	1,521,200,000		1,521,200,000
Callable structured notes amortized costs	0		0
Debt Securities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Interest Receivable	38,100,000		38,100,000		$ 38,900,000
Commercial Real Estate Non Owner Occupied Loans [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		45,200,000		17,300,000
Provision charged to operating expense		(8,800,000)		(2,100,000)
Loans Charged-Off(2)		0		(2,900,000)
Ending balance		29,500,000		29,500,000
Provisional ACL Recorded for PCD loans		(6,900,000)		17,200,000
Financing Receivable, Allowance for Credit Loss, Recovery		0		0
Agricultural Financing Receivable [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2,400,000	(1,000,000.0)	3,200,000	300,000
Provision charged to operating expense	200,000	6,300,000	(900,000)	5,800,000
Loans Charged-Off(2)	0	(100,000)	0	(5,400,000)
Ending balance	2,700,000	6,500,000	2,700,000	6,500,000
Provisional ACL Recorded for PCD loans		1,100,000		4,500,000
Financing Receivable, Allowance for Credit Loss, Recovery	100,000	200,000	400,000	1,300,000
Commercial and Floor Plans [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		52,900,000		27,100,000
Provision charged to operating expense		1,900,000		20,300,000
Loans Charged-Off(2)		(1,100,000)		(5,300,000)
Ending balance		54,100,000		54,100,000
Provisional ACL Recorded for PCD loans		0		11,200,000
Financing Receivable, Allowance for Credit Loss, Recovery		400,000		800,000
Commercial Real Estate Owner Occupied [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		25,200,000		13,300,000
Provision charged to operating expense		1,400,000		6,000,000.0
Loans Charged-Off(2)		0		(2,200,000)
Ending balance		26,600,000		26,600,000
Provisional ACL Recorded for PCD loans		0		9,500,000
Financing Receivable, Allowance for Credit Loss, Recovery		0		0
Commercial Real Estate Multi-family [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		54,600,000		13,300,000
Provision charged to operating expense		(2,900,000)		8,500,000
Loans Charged-Off(2)		0		0
Ending balance		33,400,000		33,400,000
Provisional ACL Recorded for PCD loans		(19,000,000.0)		10,900,000
Financing Receivable, Allowance for Credit Loss, Recovery		700,000		700,000
Commercial real estate
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		125,000,000.0		43,900,000
Provision charged to operating expense		(10,300,000)		12,400,000
Loans Charged-Off(2)		0	(4,600,000)	(5,100,000)
Ending balance		89,500,000		89,500,000
Provisional ACL Recorded for PCD loans		(25,900,000)		37,600,000
Financing Receivable, Allowance for Credit Loss, Recovery		700,000		700,000
Land Acquisition And Development Construction Financing Receivable [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		500,000		500,000
Provision charged to operating expense		200,000		(600,000)
Loans Charged-Off(2)		0		(2,700,000)
Ending balance		800,000		800,000
Provisional ACL Recorded for PCD loans		0		3,400,000
Financing Receivable, Allowance for Credit Loss, Recovery		100,000		200,000
Residential construction
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		3,300,000		2,400,000
Provision charged to operating expense		100,000		1,000,000.0
Loans Charged-Off(2)		0		0
Ending balance		3,400,000		3,400,000
Provisional ACL Recorded for PCD loans		0		0
Financing Receivable, Allowance for Credit Loss, Recovery		0		0
Commercial construction
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		10,200,000		6,000,000.0
Provision charged to operating expense		4,700,000		8,700,000
Loans Charged-Off(2)		0		0
Ending balance		14,900,000		14,900,000
Provisional ACL Recorded for PCD loans		0		200,000
Financing Receivable, Allowance for Credit Loss, Recovery		0		0
Construction Loans [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		14,000,000.0		8,900,000
Provision charged to operating expense		5,000,000.0		9,100,000
Loans Charged-Off(2)		0		(2,700,000)
Ending balance		19,100,000		19,100,000
Provisional ACL Recorded for PCD loans		0		3,600,000
Financing Receivable, Allowance for Credit Loss, Recovery		100,000		200,000
Residential Real Estate 1-4 Family [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		18,700,000		13,400,000
Provision charged to operating expense		(700,000)		4,500,000
Loans Charged-Off(2)		0		(100,000)
Ending balance		18,200,000		18,200,000
Provisional ACL Recorded for PCD loans		0		100,000
Financing Receivable, Allowance for Credit Loss, Recovery		200,000		300,000
Home Equity Line of Credit [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		1,400,000		1,200,000
Provision charged to operating expense		(100,000)		0
Loans Charged-Off(2)		0		0
Ending balance		1,500,000		1,500,000
Provisional ACL Recorded for PCD loans		0		0
Financing Receivable, Allowance for Credit Loss, Recovery		200,000		300,000
Residential Real Estate [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		20,100,000		14,600,000
Provision charged to operating expense		(800,000)		4,500,000
Loans Charged-Off(2)		0	(500,000)	(100,000)
Ending balance		19,700,000		19,700,000
Provisional ACL Recorded for PCD loans		0		100,000
Financing Receivable, Allowance for Credit Loss, Recovery		400,000		600,000
Agricultural Real Estate Financing Receivable [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		10,500,000		1,900,000
Provision charged to operating expense		(5,100,000)		1,300,000
Loans Charged-Off(2)		(100,000)	0	(200,000)
Ending balance		5,400,000		5,400,000
Provisional ACL Recorded for PCD loans		0		2,300,000
Financing Receivable, Allowance for Credit Loss, Recovery		100,000		100,000
Real Estate Financing Receivable [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	147,500,000	169,600,000	138,700,000	69,300,000
Provision charged to operating expense	20,400,000	(11,200,000)	33,800,000	27,300,000
Loans Charged-Off(2)	(10,000,000.0)	(100,000)	(14,800,000)	(8,100,000)
Ending balance	158,700,000	133,700,000	158,700,000	133,700,000
Provisional ACL Recorded for PCD loans		(25,900,000)		43,600,000
Financing Receivable, Allowance for Credit Loss, Recovery	800,000	1,300,000	1,000,000.0	1,600,000
Consumer Indirect Financing Receivable [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		13,500,000		14,300,000
Provision charged to operating expense		(400,000)		(700,000)
Loans Charged-Off(2)		(800,000)	(3,400,000)	(1,700,000)
Ending balance		13,100,000		13,100,000
Provisional ACL Recorded for PCD loans		0		0
Financing Receivable, Allowance for Credit Loss, Recovery		800,000		1,200,000
Direct consumer
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		4,600,000		4,600,000
Provision charged to operating expense		500,000		400,000
Loans Charged-Off(2)		(600,000)	(1,900,000)	(1,400,000)
Ending balance		5,000,000.0		5,000,000.0
Provisional ACL Recorded for PCD loans		0		0
Financing Receivable, Allowance for Credit Loss, Recovery		500,000		1,400,000
Credit Card Receivable [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		2,300,000		2,200,000
Provision charged to operating expense		700,000		1,300,000
Loans Charged-Off(2)		(900,000)	(1,400,000)	(1,500,000)
Ending balance		2,200,000		2,200,000
Provisional ACL Recorded for PCD loans		0		0
Financing Receivable, Allowance for Credit Loss, Recovery		100,000		200,000
Consumer
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	21,800,000	20,400,000	23,300,000	21,100,000
Provision charged to operating expense	(6,200,000)	800,000	(5,500,000)	1,000,000.0
Loans Charged-Off(2)	(3,300,000)	(2,300,000)	(6,700,000)	(4,600,000)
Ending balance	13,700,000	20,300,000	13,700,000	20,300,000
Provisional ACL Recorded for PCD loans		0		0
Financing Receivable, Allowance for Credit Loss, Recovery	1,400,000	1,400,000	2,600,000	2,800,000
Commercial Purpose secured by 1-4 Family [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		5,000,000.0		4,400,000
Provision charged to operating expense		400,000		800,000
Loans Charged-Off(2)		0		0
Ending balance		5,500,000		5,500,000
Provisional ACL Recorded for PCD loans		0		200,000
Financing Receivable, Allowance for Credit Loss, Recovery		100,000		100,000
Commercial Borrower [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		300,000		100,000
Provision charged to operating expense		100,000		400,000
Loans Charged-Off(2)		(100,000)		(200,000)
Ending balance		300,000		300,000
Provisional ACL Recorded for PCD loans		0		0
Financing Receivable, Allowance for Credit Loss, Recovery		0		0
Commercial Portfolio Segment [Member]
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	54,400,000	58,200,000	54,900,000	31,600,000
Provision charged to operating expense	(4,500,000)	2,400,000	(5,300,000)	21,500,000
Loans Charged-Off(2)	(800,000)	(1,200,000)	(1,500,000)	(5,500,000)
Ending balance	49,500,000	59,900,000	49,500,000	59,900,000
Provisional ACL Recorded for PCD loans		0		11,400,000
Financing Receivable, Allowance for Credit Loss, Recovery	$ 400,000	$ 500,000	$ 1,400,000	$ 900,000