Loans (Analysis of the Aged Loan Portfolio) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	$ 24,021	$ 34,806
Total Loans	9,693,116	9,427,660
Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	3,019	7,712
Total Loans	4,101,071	4,062,313
Commercial Business [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	10,745	13,222
Total Loans	3,738,288	3,597,968
Agriculture [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	9,034	11,614
Total Loans	797,580	779,627
Construction [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	0	217
Total Loans	300,303	268,663
One-to-Four Family Residential [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	1,179	2,001
Total Loans	724,151	683,570
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	44	40
Total Loans	31,723	35,519
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	9,651,747	9,364,697
Financial Asset, Not Past Due | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	4,089,659	4,037,309
Financial Asset, Not Past Due | Commercial Business [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	3,724,202	3,578,905
Financial Asset, Not Past Due | Agriculture [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	785,071	767,102
Financial Asset, Not Past Due | Construction [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	300,303	268,304
Financial Asset, Not Past Due | One-to-Four Family Residential [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	720,854	677,627
Financial Asset, Not Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	31,658	35,450
Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	13,927	21,792
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	8,244	17,292
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Business [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	2,351	1,282
Financial Asset, 30 to 59 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	2,537	911
Financial Asset, 30 to 59 Days Past Due [Member] | Construction [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Financial Asset, 30 to 59 Days Past Due [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	775	2,283
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	20	24
Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	3,421	6,365
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	149	0
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Business [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	990	4,559
Financial Asset, 60 to 89 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	938	0
Financial Asset, 60 to 89 Days Past Due [Member] | Construction [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	142
Financial Asset, 60 to 89 Days Past Due [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	1,343	1,659
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	1	5
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Business [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Construction [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	17,348	28,157
Financial Asset, Past Due | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	8,393	17,292
Financial Asset, Past Due | Commercial Business [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	3,341	5,841
Financial Asset, Past Due | Agriculture [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	3,475	911
Financial Asset, Past Due | Construction [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	142
Financial Asset, Past Due | One-to-Four Family Residential [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	2,118	3,942
Financial Asset, Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 21	$ 29