Loans (Analysis of the Aged Loan Portfolio) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	$ 24,176	$ 34,806
Total Loans	9,521,385	9,427,660
Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	2,871	7,712
Total Loans	4,088,484	4,062,313
Commercial Business [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	12,105	13,222
Total Loans	3,436,351	3,597,968
Agriculture [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	7,706	11,614
Total Loans	815,985	779,627
Construction [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	0	217
Total Loans	326,569	268,663
One-to-Four Family Residential [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	1,491	2,001
Total Loans	823,877	683,570
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	3	40
Total Loans	30,119	35,519
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	9,489,455	9,364,697
Financial Asset, Not Past Due | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	4,081,036	4,037,309
Financial Asset, Not Past Due | Commercial Business [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	3,421,381	3,578,905
Financial Asset, Not Past Due | Agriculture [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	808,279	767,102
Financial Asset, Not Past Due | Construction [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	326,569	268,304
Financial Asset, Not Past Due | One-to-Four Family Residential [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	822,170	677,627
Financial Asset, Not Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	30,020	35,450
Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	5,243	21,792
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	3,803	17,292
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Business [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	1,334	1,282
Financial Asset, 30 to 59 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	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	10	2,283
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	96	24
Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	2,511	6,365
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	774	0
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Business [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	1,531	4,559
Financial Asset, 60 to 89 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	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	206	1,659
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	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	7,754	28,157
Financial Asset, Past Due | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	4,577	17,292
Financial Asset, Past Due | Commercial Business [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	2,865	5,841
Financial Asset, Past Due | Agriculture [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	0	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	216	3,942
Financial Asset, Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 96	$ 29