Loans - Purchased Credit Impaired Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loans Held for Investment
Total purchase credit impaired	$ 17,440
SBA
Loans Held for Investment
Total purchase credit impaired			$ 3,865
Business Loans | Commercial and industrial
Loans Held for Investment
Total purchase credit impaired	1,071	$ 1,585	1,990
Business Loans | Commercial owner occupied
Loans Held for Investment
Total purchase credit impaired	628	98	847
Business Loans | SBA
Loans Held for Investment
Total purchase credit impaired	7,598	4,329
Real Estate Loans
Loans Held for Investment
Total purchase credit impaired		6,896	7,029
Real Estate Loans | Commercial non-owner occupied
Loans Held for Investment
Total purchase credit impaired	0	0	0
Real Estate Loans | One-to-four family
Loans Held for Investment
Total purchase credit impaired	453	849	291
Real Estate Loans | Construction
Loans Held for Investment
Total purchase credit impaired		0
Real Estate Loans | Land
Loans Held for Investment
Total purchase credit impaired	0	35	$ 36
Consumer Loans | Consumer loans
Loans Held for Investment
Total purchase credit impaired	0
Acquired Banks
Loans Held for Investment
Total purchase credit impaired	2,182	8,889
Acquired Banks | Business Loans
Loans Held for Investment
Total purchase credit impaired	1,907	6,374
Acquired Banks | Business Loans | Commercial and industrial
Loans Held for Investment
Total purchase credit impaired	10	3,310
Acquired Banks | Business Loans | Commercial owner occupied
Loans Held for Investment
Total purchase credit impaired	632	1,262
Acquired Banks | Business Loans | SBA
Loans Held for Investment
Total purchase credit impaired	1,265	1,802
Acquired Banks | Real Estate Loans
Loans Held for Investment
Total purchase credit impaired	275	2,505
Acquired Banks | Real Estate Loans | Commercial non-owner occupied
Loans Held for Investment
Total purchase credit impaired	275	1,650
Acquired Banks | Real Estate Loans | One-to-four family
Loans Held for Investment
Total purchase credit impaired	0	255
Acquired Banks | Real Estate Loans | Construction
Loans Held for Investment
Total purchase credit impaired	0	517
Acquired Banks | Real Estate Loans | Land
Loans Held for Investment
Total purchase credit impaired	0	83
Acquired Banks | Consumer Loans | Consumer loans
Loans Held for Investment
Total purchase credit impaired	$ 0	$ 10