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 - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2020
Financing Receivable, Impaired [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	$ 58,336	$ 52,147
Interest Income Recognized	425	800
Consumer
Financing Receivable, Impaired [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	1,895	2,082
Interest Income Recognized	52	95
Consumer | Credit cards
Financing Receivable, Impaired [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	332	320
Interest Income Recognized	40	70
Consumer | Other consumer
Financing Receivable, Impaired [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	1,563	1,762
Interest Income Recognized	12	25
Real Estate
Financing Receivable, Impaired [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	25,517	25,095
Interest Income Recognized	178	354
Real Estate | Construction and development
Financing Receivable, Impaired [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	2,355	1,993
Interest Income Recognized	14	28
Real Estate | Single family residential
Financing Receivable, Impaired [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	15,486	14,351
Interest Income Recognized	105	203
Real Estate | Other commercial
Financing Receivable, Impaired [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	7,676	8,751
Interest Income Recognized	59	123
Commercial
Financing Receivable, Impaired [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	30,924	24,970
Interest Income Recognized	195	351
Commercial | Commercial
Financing Receivable, Impaired [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	29,776	23,811
Interest Income Recognized	187	335
Commercial | Agricultural
Financing Receivable, Impaired [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	1,148	1,159
Interest Income Recognized	$ 8	$ 16