Loans - Composition of Loans Held for Investment (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Consolidated Loan Portfolio [Abstract]
Outstanding Amount	$ 1,969,660		$ 1,049,698	$ 966,545
Less allowance for loan losses	15,692	$ 14,671	16,008	14,696	$ 13,834	$ 13,563
Net loans	$ 1,953,968		$ 1,033,690
Percent of Total Portfolio (as a percent)	100.00%		100.00%
Commercial real estate - owner occupied
Consolidated Loan Portfolio [Abstract]
Outstanding Amount	$ 443,128		$ 250,440	238,224
Less allowance for loan losses	$ 3,707	3,037	$ 2,943	3,001	3,142	3,042
Percent of Total Portfolio (as a percent)	22.50%		23.87%
Commercial real estate - nonowner occupied
Consolidated Loan Portfolio [Abstract]
Outstanding Amount	$ 435,181		$ 184,688	174,342
Less allowance for loan losses	$ 3,342	2,691	$ 2,145	2,140	1,969	1,862
Percent of Total Portfolio (as a percent)	22.09%		17.59%
Real estate construction
Consolidated Loan Portfolio [Abstract]
Outstanding Amount	$ 104,193		$ 91,822	79,621
Less allowance for loan losses	$ 689	877	$ 1,277	1,251	1,178	1,056
Percent of Total Portfolio (as a percent)	5.29%		8.75%
Residential real estate
Consolidated Loan Portfolio [Abstract]
Outstanding Amount	$ 512,621		$ 204,413	202,605
Less allowance for loan losses	$ 2,311	2,382	$ 2,510	2,634	2,854	2,862
Percent of Total Portfolio (as a percent)	26.03%		19.47%
Commercial
Consolidated Loan Portfolio [Abstract]
Outstanding Amount	$ 449,450		$ 311,486	264,794
Less allowance for loan losses	$ 5,557	5,595	$ 7,053	5,586	4,574	4,612
Percent of Total Portfolio (as a percent)	22.82%		29.67%
Consumer
Consolidated Loan Portfolio [Abstract]
Outstanding Amount	$ 25,087		$ 6,849	6,959
Less allowance for loan losses	$ 86	$ 89	$ 80	$ 84	$ 117	$ 129
Percent of Total Portfolio (as a percent)	1.27%		0.65%