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	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 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	$ 64,550	$ 56,612
Interest Income Recognized	400	1,200
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	2,026	2,100
Interest Income Recognized	49	143
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	423	370
Interest Income Recognized	40	110
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	1,603	1,730
Interest Income Recognized	9	33
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	29,631	27,123
Interest Income Recognized	172	526
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	1,972	1,946
Interest Income Recognized	10	38
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	15,920	14,812
Interest Income Recognized	85	287
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	11,739	10,365
Interest Income Recognized	77	201
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	32,893	27,389
Interest Income Recognized	179	531
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	32,020	26,379
Interest Income Recognized	176	511
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	873	1,010
Interest Income Recognized	$ 3	$ 20