Selected Quarterly Consolidated Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Quarterly Financial Information Disclosure [Abstract]
Interest and dividend income	$ 39,374	$ 40,834	$ 42,612	$ 47,116	$ 47,383	$ 49,527	$ 50,559	$ 50,194	$ 169,936		$ 197,663		$ 176,407
Interest expense	7,131	9,180	11,667	14,514	15,389	16,549	16,701	15,610	42,492		64,249		44,117
Net interest income (expense)	32,243	31,654	30,945	32,602	31,994	32,978	33,858	34,584	127,444	[1]	133,414	[1]	132,290	[1]
Provision for credit losses	1,781	1,325	2,200	7,036	0	400	525	650	12,342		1,575		1,550
Net interest income after provision for credit losses	30,462	30,329	28,745	25,566	31,994	32,578	33,333	33,934	115,102		131,839		130,740
Noninterest income	27,727	25,468	26,320	19,927	16,618	18,342	16,753	15,367	99,442	[1]	67,080	[1]	62,114	[1]
Noninterest expense	34,109	32,344	28,478	30,453	28,755	26,870	28,151	26,964	125,384		110,740		106,162
Income before income taxes	24,080	23,453	26,587	15,040	19,857	24,050	21,935	22,337	89,160		88,179		86,692
Income tax expense	5,514	5,131	5,547	3,139	4,321	5,236	4,662	4,842	19,331		19,061		18,260
Net income	18,566	18,322	21,040	11,901	15,536	18,814	17,273	17,495	69,829		69,118		68,432
Net income available to common shareholders	$ 18,524	$ 18,285	$ 21,000	$ 11,869	$ 15,502	$ 18,778	$ 17,238	$ 17,461	$ 69,678		$ 68,979		$ 68,288
Weighted average common shares outstanding - basic	17,264	17,260	17,257	17,345	17,351	17,338	17,330	17,304	17,282		17,331		17,272
Weighted average common shares outstanding - diluted	17,360	17,317	17,292	17,441	17,436	17,414	17,405	17,401	17,402		17,414		17,391
Basic earnings per common share (in dollars per share)	$ 1.07	$ 1.06	$ 1.22	$ 0.68	$ 0.89	$ 1.08	$ 0.99	$ 1.01	$ 4.03		$ 3.98		$ 3.95
Diluted earnings per common share (in dollars per share)	1.07	1.06	1.21	0.68	0.89	1.08	0.99	1.00	4.00		3.96		3.93
Cash dividends declared per share (in dollars per share)	$ 0.52	$ 0.51	$ 0.51	$ 0.51	$ 0.51	$ 0.51	$ 0.51	$ 0.47	$ 2.05		$ 2.00		$ 1.76

[1] As reported in the Consolidated Statements of Income.