Loans and Allowance for Loan Losses - Nonaccrual Loans, Excluding Loans Acquired, Segregated by Class of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	$ 155,863	$ 93,330
Consumer
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	2,376	2,087
Consumer | Credit cards
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	265	382
Consumer | Other consumer
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	2,111	1,705
Real Estate
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	73,861	49,566
Real Estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	6,604	5,289
Real Estate | Single family residential
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	30,829	27,695
Real Estate | Other commercial
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	36,428	16,582
Commercial
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	79,626	41,677
Commercial | Commercial
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	78,944	40,924
Commercial | Agricultural
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	$ 682	$ 753