Loans (Analysis of the Aged Loan Portfolio) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 10,641,937	$ 9,427,660
Nonaccrual Loans	23,041	34,806
Commercial Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,981,263	4,062,313
Nonaccrual Loans	1,872	7,712
Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,423,268	3,597,968
Nonaccrual Loans	13,321	13,222
Agriculture
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	795,715	779,627
Nonaccrual Loans	5,396	11,614
Construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	384,755	268,663
Nonaccrual Loans	0	217
Real estate: One-to-four family residential
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,013,908	683,570
Nonaccrual Loans	2,433	2,001
Consumer Loan
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	43,028	35,519
Nonaccrual Loans	19	40
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,611,528	9,364,697
Financial Asset, Not Past Due | Commercial Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,977,781	4,037,309
Financial Asset, Not Past Due | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,406,539	3,578,905
Financial Asset, Not Past Due | Agriculture
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	789,112	767,102
Financial Asset, Not Past Due | Construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	384,755	268,304
Financial Asset, Not Past Due | Real estate: One-to-four family residential
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,010,343	677,627
Financial Asset, Not Past Due | Consumer Loan
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	42,998	35,450
Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,860	21,792
Financial Asset, 30 to 59 Days Past Due | Commercial Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	17,292
Financial Asset, 30 to 59 Days Past Due | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,721	1,282
Financial Asset, 30 to 59 Days Past Due | Agriculture
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,207	911
Financial Asset, 30 to 59 Days Past Due | Construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, 30 to 59 Days Past Due | Real estate: One-to-four family residential
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	921	2,283
Financial Asset, 30 to 59 Days Past Due | Consumer Loan
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	11	24
Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,508	6,365
Financial Asset, 60 to 89 Days Past Due | Commercial Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,610	0
Financial Asset, 60 to 89 Days Past Due | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	687	4,559
Financial Asset, 60 to 89 Days Past Due | Agriculture
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, 60 to 89 Days Past Due | Construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	142
Financial Asset, 60 to 89 Days Past Due | Real estate: One-to-four family residential
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	211	1,659
Financial Asset, 60 to 89 Days Past Due | Consumer Loan
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	5
Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due | Commercial Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due | Agriculture
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due | Construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due | Real estate: One-to-four family residential
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due | Consumer Loan
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,368	28,157
Financial Asset, Past Due | Commercial Real Estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,610	17,292
Financial Asset, Past Due | Commercial Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,408	5,841
Financial Asset, Past Due | Agriculture
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,207	911
Financial Asset, Past Due | Construction
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	142
Financial Asset, Past Due | Real estate: One-to-four family residential
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,132	3,942
Financial Asset, Past Due | Consumer Loan
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 11	$ 29