Quarterly Financial Data -- Unaudited (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Interest income	$ 25,313	$ 24,614	$ 25,446	$ 24,182	$ 23,011	$ 18,623	$ 16,883	$ 16,979
Interest expense	1,838	1,741	1,493	1,410	1,487	1,000	913	892	$ 6,482	$ 4,292	$ 3,499
Net interest income	23,475	22,873	23,953	22,772	21,524	17,623	15,970	16,087	93,073	71,204	55,752
Provision for loan losses	2,411	1,489	1,840	1,722	899	1,081	733	113
Net interest income after provision for loan losses	21,064	21,384	22,113	21,050	20,625	16,542	15,237	15,974	85,611	68,378	54,434
Other income	7,210	7,661	7,969	7,496	6,911	6,898	6,459	6,644	30,336	26,912	20,544
Other expense	19,152	17,912	17,955	19,202	16,876	15,320	14,143	15,171	74,221	61,510	49,248
Income before income taxes	9,122	11,133	12,127	9,344	10,660	8,120	7,553	7,447	41,726	33,780	25,730
Total	4,497	3,538	3,927	3,080	3,863	2,812	2,624	2,641	15,042	11,940	9,218
Net income					6,797	5,308	4,929	4,806	26,684	21,840	16,512
Dividends on preferred shares					0	0	275	550	0	825	2,200
Net income available to common stockholders	$ 4,625	$ 7,595	$ 8,200	$ 6,264	$ 6,797	$ 5,308	$ 4,654	$ 4,256	$ 26,684	$ 21,015	$ 14,312
Basic earnings per common share	$ 0.37	$ 0.61	$ 0.66	$ 0.50	$ 0.55	$ 0.51	$ 0.51	$ 0.50	$ 2.13	$ 2.07	$ 1.84
Diluted earnings per common share	$ 0.37	$ 0.61	$ 0.66	$ 0.50	$ 0.55	$ 0.51	$ 0.50	$ 0.49	$ 2.13	$ 2.05	$ 1.81