Summarized Quarterly Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summarized Quarterly Information (Unaudited) [Abstract]
Total interest income	$ 37,923	$ 39,013	$ 39,306	$ 40,862	$ 42,289	$ 43,609	$ 43,621	$ 40,576
Total interest expense	3,615	3,894	4,446	6,226	7,168	7,855	7,572	6,662	$ 18,181	$ 29,257	$ 21,652
Net interest income	34,308	35,119	34,860	34,636	35,121	35,754	36,049	33,914	138,923	140,838	(129,612)
Provision (recovery) for credit losses (a)	(7,277)	4,728	11,834	16,969	1,136	1,005	626	(263)
Net gain on investment securities	(751)	2	62	319	94	97	(57)	30	(368)	164	(146)
Net loss on asset disposals and other transactions	(53)	(28)	(122)	(87)	(229)	(78)	(293)	(182)	(290)	(782)	(334)
Total non-interest income excluding net gains and losses (b)	17,305	16,796	14,724	15,505	17,298	16,374	15,639	15,581
Amortization of other intangible assets	909	857	728	729	888	953	824	694	3,223	3,359	3,338
Acquisition-related expenses	77	335	47	30	65	199	6,770	253
Other expense	32,264	33,123	31,030	33,566	32,568	31,841	31,282	30,913
Applicable income tax expense	4,263	2,636	1,136	(156)	2,767	3,281	2,238	3,377	7,879	11,663	8,686
Net income	$ 20,573	$ 10,210	$ 4,749	$ (765)	$ 14,860	$ 14,868	$ 9,598	$ 14,369	$ 34,767	$ 53,695	$ 46,255
Earnings per common share – basic	$ 1.06	$ 0.52	$ 0.24	$ (0.04)	$ 0.72	$ 0.72	$ 0.47	$ 0.74	$ 1.74	$ 2.65	$ 2.42
Earnings per common share – diluted	$ 1.05	$ 0.51	$ 0.23	$ (0.04)	$ 0.72	$ 0.72	$ 0.46	$ 0.73	$ 1.73	$ 2.63	$ 2.41
Weighted-average number of common shares outstanding – basic	19,302,919	19,504,503	19,720,315	20,367,564	20,407,505	20,415,245	20,277,028	19,366,008	19,721,772	20,120,119	18,991,768
Weighted-average number of common shares outstanding – diluted	19,442,284	19,637,689	19,858,880	20,538,214	20,599,127	20,595,769	20,442,366	19,508,868	19,843,806	20,273,725	19,122,260