Loans Held for Investment - Purchased Credit Impaired Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Loans Held for Investment
Unpaid Principal Balance	$ 25,750	$ 17,440
Business loans | Commercial and industrial
Loans Held for Investment
Unpaid Principal Balance	3,417	1,071
Business loans | Commercial owner occupied
Loans Held for Investment
Unpaid Principal Balance	564	628
Business loans | SBA
Loans Held for Investment
Unpaid Principal Balance	9,059	7,598
Real estate loans | Commercial non-owner occupied
Loans Held for Investment
Unpaid Principal Balance	3,654
Acquired Banks
Loans Held for Investment
Unpaid Principal Balance	1,768	2,182
Acquired Banks | Business loans | Commercial and industrial
Loans Held for Investment
Unpaid Principal Balance	0	10
Acquired Banks | Business loans | Commercial owner occupied
Loans Held for Investment
Unpaid Principal Balance	578	632
Acquired Banks | Business loans | SBA
Loans Held for Investment
Unpaid Principal Balance	1,190	1,265
Acquired Banks | Real estate loans | Commercial non-owner occupied
Loans Held for Investment
Unpaid Principal Balance	$ 0	$ 275