Loans - Purchased Credit Impaired Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans Held for Investment
Total purchase credit impaired	$ 7,029	$ 4,319	$ 1,913
Business loans: Commercial and industrial
Loans Held for Investment
Total purchase credit impaired	1,990	578	0
Business loans: Commercial owner occupied
Loans Held for Investment
Total purchase credit impaired	847	883	440
Real estate loans: Commercial non-owner occupied
Loans Held for Investment
Total purchase credit impaired	0	329	1,217
Real estate loans: One-to-four family
Loans Held for Investment
Total purchase credit impaired	291	98	$ 256
Acquired Banks
Loans Held for Investment
Total purchase credit impaired	4,559	3,346
Acquired Banks | Other loans
Loans Held for Investment
Total purchase credit impaired	393	0
Acquired Banks | Commercial Portfolio Segment | Business loans: Commercial and industrial
Loans Held for Investment
Total purchase credit impaired	2,586	289
Acquired Banks | Commercial Portfolio Segment | Business loans: Commercial owner occupied
Loans Held for Investment
Total purchase credit impaired	491	884
Acquired Banks | Consumer Portfolio Segment | Real estate loans: Commercial non-owner occupied
Loans Held for Investment
Total purchase credit impaired	1,088	2,088
Acquired Banks | Consumer Portfolio Segment | Real estate loans: One-to-four family
Loans Held for Investment
Total purchase credit impaired	$ 1	$ 85