Quarterly Results of Operations (Unaudited) (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	[1]	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Interest income		$ 40,453	$ 38,557	$ 37,089	$ 35,278	$ 35,040		$ 34,710	$ 33,940	$ 32,414	$ 151,377	$ 136,104	$ 129,626
Interest expense		8,866	8,134	7,608	6,376	5,381		5,550	5,314	4,559	30,984	20,804	16,554
Net interest income		31,587	30,423	29,481	28,902	29,659		29,160	28,626	27,855	120,393	115,300	113,072
Provision for credit losses		7	354	983	(497)	238		817	1,401	579	847	3,035	5,258
Non-interest income		9,479	10,392	9,501	8,804	9,840		10,299	9,888	8,572	38,176	38,599	39,621
Non-interest expense		23,580	23,166	22,895	22,304	23,099		21,825	22,158	21,428	91,945	88,510	89,896
Income before income tax expense		17,479	17,295	15,104	15,899	16,162		16,817	14,955	14,420	65,777	62,354	57,539
Income tax expense		3,502	3,238	2,887	3,079	19,335		5,478	4,721	4,344	12,706	33,878	17,472
Net income		$ 13,977	$ 14,057	$ 12,217	$ 12,820	$ (3,173)		$ 11,339	$ 10,234	$ 10,076	$ 53,071	$ 28,476	$ 40,067
Per common share:
Basic earnings per share		$ 0.90	$ 0.90	$ 0.78	$ 0.82	$ (0.20)		$ 0.72	$ 0.66	$ 0.65	$ 3.40	$ 1.83	$ 2.59
Diluted earnings per share		0.89	$ 0.90	$ 0.78	$ 0.82	$ (0.20)		$ 0.72	$ 0.66	$ 0.64	$ 3.39	$ 1.82	$ 2.57
Change in federal corporate income tax rate(1)	[2]										$ 0	$ 14,263	$ 0
Impact of Restatement on Earnings Per Share, Diluted		$ 0.91

[1] (1) In the fourth quarter of 2017, the Company recognized $14.3 million of additional income tax expense upon the revaluation of its deferred tax assets and liabilities upon enactment of the Tax Act on December 22, 2017, which lowered the federal corporate tax rate from 35.0% to 21.0%, effective January 1, 2018. The impact to fourth quarter 2017 basic and diluted EPS was $0.91 per share.

[2] (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.