Loans (Analysis of Loan Portfolio by Major Types of Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator - interest written off on nonaccrual loans [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 10,759,684	$ 10,641,937
Financing Receivable, Allowance for Credit Loss	(146,949)	(155,578)	$ (148,294)	$ (149,140)
Loans and Leases Receivable, Net Amount	10,612,735	10,486,359
Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator - interest written off on nonaccrual loans [Line Items]
Loans and Leases Receivable, Net of Deferred Income	5,047,472	4,981,263
Financing Receivable, Allowance for Credit Loss	(57,307)	(61,254)	(57,050)	(68,934)
Commercial Business [Member]
Financing Receivable, Credit Quality Indicator - interest written off on nonaccrual loans [Line Items]
Loans and Leases Receivable, Net of Deferred Income	3,492,307	3,423,268
Financing Receivable, Allowance for Credit Loss	(50,474)	(54,712)	(58,405)	(45,250)
Agriculture [Member]
Financing Receivable, Credit Quality Indicator - interest written off on nonaccrual loans [Line Items]
Loans and Leases Receivable, Net of Deferred Income	765,319	795,715
Financing Receivable, Allowance for Credit Loss	(8,010)	(8,148)	(9,487)	(9,052)
Construction [Member]
Financing Receivable, Credit Quality Indicator - interest written off on nonaccrual loans [Line Items]
Loans and Leases Receivable, Net of Deferred Income	409,242	384,755
Financing Receivable, Allowance for Credit Loss	(5,399)	(5,397)	(6,551)	(7,636)
One-to-Four Family Residential [Member]
Financing Receivable, Credit Quality Indicator - interest written off on nonaccrual loans [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,003,157	1,013,908
Financing Receivable, Allowance for Credit Loss	(24,356)	(24,123)	(15,638)	(16,875)
Consumer Loan [Member]
Financing Receivable, Credit Quality Indicator - interest written off on nonaccrual loans [Line Items]
Loans and Leases Receivable, Net of Deferred Income	42,187	43,028
Financing Receivable, Allowance for Credit Loss	$ (1,403)	$ (1,944)	$ (1,163)	$ (1,393)

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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