Loans and Allowance for Credit Losses - Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired, Segregated by Class of Loans (Details) - Loans, Excluding Acquired Loans $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	$ 90,639
Recorded Investment With No Allowance	33,043
Recorded Investment With Allowance	35,889
Total Recorded Investment	68,932
Related Allowance	5,747
Average Investment in Impaired Loans	59,076
Interest Income Recognized	1,500
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	1,919
Recorded Investment With No Allowance	1,760
Recorded Investment With Allowance	0
Total Recorded Investment	1,760
Related Allowance	0
Average Investment in Impaired Loans	2,032
Interest Income Recognized	91
Consumer | Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	382
Recorded Investment With No Allowance	382
Recorded Investment With Allowance	0
Total Recorded Investment	382
Related Allowance	0
Average Investment in Impaired Loans	373
Interest Income Recognized	50
Consumer | Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	1,537
Recorded Investment With No Allowance	1,378
Recorded Investment With Allowance	0
Total Recorded Investment	1,378
Related Allowance	0
Average Investment in Impaired Loans	1,659
Interest Income Recognized	41
Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	34,759
Recorded Investment With No Allowance	24,318
Recorded Investment With Allowance	6,775
Total Recorded Investment	31,093
Related Allowance	740
Average Investment in Impaired Loans	27,917
Interest Income Recognized	690
Real Estate | Construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	4,648
Recorded Investment With No Allowance	4,466
Recorded Investment With Allowance	72
Total Recorded Investment	4,538
Related Allowance	4
Average Investment in Impaired Loans	2,464
Interest Income Recognized	61
Real Estate | Single family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	19,466
Recorded Investment With No Allowance	15,139
Recorded Investment With Allowance	2,963
Total Recorded Investment	18,102
Related Allowance	42
Average Investment in Impaired Loans	15,470
Interest Income Recognized	382
Real Estate | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	10,645
Recorded Investment With No Allowance	4,713
Recorded Investment With Allowance	3,740
Total Recorded Investment	8,453
Related Allowance	694
Average Investment in Impaired Loans	9,983
Interest Income Recognized	247
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	53,961
Recorded Investment With No Allowance	6,965
Recorded Investment With Allowance	29,114
Total Recorded Investment	36,079
Related Allowance	5,007
Average Investment in Impaired Loans	29,127
Interest Income Recognized	719
Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	53,436
Recorded Investment With No Allowance	6,582
Recorded Investment With Allowance	28,998
Total Recorded Investment	35,580
Related Allowance	5,007
Average Investment in Impaired Loans	28,219
Interest Income Recognized	697
Commercial | Agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	525
Recorded Investment With No Allowance	383
Recorded Investment With Allowance	116
Total Recorded Investment	499
Related Allowance	0
Average Investment in Impaired Loans	908
Interest Income Recognized	$ 22