Selected Quarterly Consolidated Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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 and dividend income	$ 47,383	$ 49,527	$ 50,559	$ 50,194	$ 47,517	$ 45,164	$ 43,286	$ 40,440	$ 197,663		$ 176,407		$ 149,586
Interest expense	15,389	16,549	16,701	15,610	13,639	11,715	10,175	8,588	64,249		44,117		30,055
Net interest income	31,994	32,978	33,858	34,584	33,878	33,449	33,111	31,852	133,414	[1]	132,290	[1]	119,531	[1]
Provision for loan losses	0	400	525	650	800	350	400	0	1,575		1,550		2,600
Net interest income after provision for loan losses	31,994	32,578	33,333	33,934	33,078	33,099	32,711	31,852	131,839		130,740		116,931
Noninterest income	16,618	18,342	16,753	15,367	15,163	15,215	15,993	15,743	67,080	[1]	62,114	[1]	64,809	[1]
Noninterest expense	28,755	26,870	28,151	26,964	26,682	26,062	26,288	27,130	110,740		106,162		104,100
Income before income taxes	19,857	24,050	21,935	22,337	21,559	22,252	22,416	20,465	88,179		86,692		77,640
Income tax expense	4,321	5,236	4,662	4,842	4,523	4,741	4,742	4,254	19,061		18,260		31,715
Net income	15,536	18,814	17,273	17,495	17,036	17,511	17,674	16,211	69,118		68,432		45,925
Net income available to common shareholders	$ 15,502	$ 18,778	$ 17,238	$ 17,461	$ 17,004	$ 17,475	$ 17,636	$ 16,173	$ 68,979		$ 68,288		$ 45,817
Weighted average common shares outstanding - basic	17,351	17,338	17,330	17,304	17,297	17,283	17,272	17,234	17,331		17,272		17,207
Weighted average common shares outstanding - diluted	17,436	17,414	17,405	17,401	17,385	17,382	17,387	17,345	17,414		17,391		17,338
Basic earnings per common share (in dollars per share)	$ 0.89	$ 1.08	$ 0.99	$ 1.01	$ 0.98	$ 1.01	$ 1.02	$ 0.94	$ 3.98		$ 3.95		$ 2.66
Diluted earnings per common share (in dollars per share)	0.89	1.08	0.99	1.00	0.98	1.01	1.01	0.93	3.96		3.93		2.64
Cash dividends declared per share (in dollars per share)	$ 0.51	$ 0.51	$ 0.51	$ 0.47	$ 0.47	$ 0.43	$ 0.43	$ 0.43	$ 2.00		$ 1.76		$ 1.54

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