Quarterly Financial Data (Unaudited) - Selected Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Data (Unaudited)
Interest income	$ 35,378	$ 34,610	$ 31,980	$ 27,877	$ 28,152	$ 27,955	$ 26,107	$ 24,697	$ 129,845	$ 106,911	$ 94,431
Interest expense	2,318	2,159	1,816	1,529	1,708	1,634	1,174	871	7,822	5,387	3,211
Net interest income	33,060	32,451	30,164	26,348	26,444	26,321	24,933	23,826	122,023	101,524	91,220
Provision (credit) for loan losses	142	(425)	7,198	506	(291)	115	(46)	321	7,421	99	1,237
Net interest income after provision for loan losses	32,918	32,876	22,966	25,842	26,735	26,206	24,979	23,505	114,602	101,425	89,983
Noninterest income	2,393	2,206	2,780	2,195	2,564	2,460	2,293	2,295	9,574	9,612	11,625
Noninterest expense	16,941	17,728	24,862	15,990	15,322	14,834	15,254	15,328	75,521	60,738	57,639
Income before income taxes	18,370	17,354	884	12,047	13,977	13,832	12,018	10,472	48,655	50,299	43,969
Income tax expense (benefit)	5,138	4,979	(31)	3,238	12,719	5,249	4,569	3,934	13,324	26,471	16,588
Net income	$ 13,232	$ 12,375	$ 915	$ 8,809	$ 1,258	$ 8,583	$ 7,449	$ 6,538	$ 35,331	$ 23,828	$ 27,381
Earnings per common share:
Basic (in dollars per share)	$ 0.31	$ 0.29	$ 0.02	$ 0.23	$ 0.03	$ 0.22	$ 0.20	$ 0.17	$ 0.85	$ 0.63	$ 0.72
Diluted (in dollars per share)	$ 0.30	$ 0.28	$ 0.02	$ 0.23	$ 0.03	$ 0.22	$ 0.19	$ 0.17	$ 0.84	$ 0.62	$ 0.72