Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Interest income		$ 41,552	$ 42,520	$ 42,437	$ 42,009	$ 40,453	$ 38,557	$ 37,089	$ 35,278	$ 168,518	$ 151,377	$ 136,104
Interest expense		9,313	10,597	10,864	10,114	8,866	8,134	7,608	6,376	40,888	30,984	20,804
Net interest income		32,239	31,923	31,573	31,895	31,587	30,423	29,481	28,902	127,630	120,393	115,300
Provision for credit losses		214	730	1,173	744	7	354	983	(497)	2,861	847	3,035
Non-interest income		11,948	10,739	10,037	9,389	9,479	10,392	9,501	8,804	42,113	38,176	38,599
Non-interest expense		24,814	23,748	23,958	22,783	23,580	23,166	22,895	22,304	95,303	91,945	88,510
Income before income tax expense		19,159	18,184	16,479	17,757	17,479	17,295	15,104	15,899	71,579	65,777	62,354
Income tax expense		3,921	3,696	3,275	3,484	3,502	3,238	2,887	3,079	14,376	12,706	33,878
Net income		$ 15,238	$ 14,488	$ 13,204	$ 14,273	$ 13,977	$ 14,057	$ 12,217	$ 12,820	$ 57,203	$ 53,071	$ 28,476
Per common share:
Basic earnings per share		$ 1.00	$ 0.94	$ 0.85	$ 0.91	$ 0.90	$ 0.90	$ 0.78	$ 0.82	$ 3.70	$ 3.40	$ 1.83
Diluted earnings per share		$ 0.99	$ 0.94	$ 0.85	$ 0.91	$ 0.89	$ 0.90	$ 0.78	$ 0.82	$ 3.69	$ 3.39	$ 1.82
Change in federal corporate income tax rate(1)	[1]									$ 0	$ 0	$ 14,263

[1] (1)On December 22, 2017, the Tax Act was enacted, reducing the U.S. federal corporate income tax rate from 35.0% to 21.0%. The Company recognized the effect of the tax law changes in the period of enactment, which resulted in a reduction to net deferred tax assets and a corresponding charge to income tax expense of $14.3 million.