Loans Acquired - Nonaccrual Acquired Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	$ 60,925	$ 34,201
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	1,893	2,455
Consumer | Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	1,555	2,159
Real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	26,506	20,413
Real estate | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	2,570	1,269
Real estate | Single family residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	15,324	11,939
Real estate | Other commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	8,612	7,205
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	32,526	11,333
Commercial | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	31,409	10,049
Commercial | Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	1,117	1,284
Loans Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	18,731	21,640
Loans Acquired | Consumer | Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	149	140
Loans Acquired | Real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	15,445	7,884
Loans Acquired | Real estate | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	130	114
Loans Acquired | Real estate | Single family residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	6,342	6,603
Loans Acquired | Real estate | Other commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	8,973	1,167
Loans Acquired | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	3,137	13,616
Loans Acquired | Commercial | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	3,117	13,578
Loans Acquired | Commercial | Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans in nonaccrual status	$ 20	$ 38