Selected Quarterly Consolidated Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Interest and dividend income	$ 35,055	$ 33,256	$ 32,190	$ 32,969	$ 31,477	$ 31,526	$ 31,510	$ 31,237	$ 133,470	$ 125,750	$ 121,117
Interest expense	6,467	5,877	5,414	5,234	5,222	5,529	5,482	5,535	22,992	21,768	21,612
Net interest income	28,588	27,379	26,776	27,735	26,255	25,997	26,028	25,702	110,478	103,982	99,505
Provision for loan losses	2,900	1,800	450	500	750	200	100	0	5,650	1,050	1,850
Net interest income after provision for loan losses	25,688	25,579	26,326	27,235	25,505	25,797	25,928	25,702	104,828	102,932	97,655
Noninterest income	17,320	17,261	15,914	14,634	15,146	13,913	15,261	14,020	65,129	58,340	59,015
Noninterest expense	24,973	24,650	26,030	25,450	24,561	24,538	24,299	23,531	101,103	96,929	96,847
Income before income taxes	18,035	18,190	16,210	16,419	16,090	15,172	16,890	16,191	68,854	64,343	59,823
Income tax expense	5,873	5,863	5,153	5,484	5,346	4,964	5,387	5,181	22,373	20,878	18,999
Net income	$ 12,162	$ 12,327	$ 11,057	$ 10,935	$ 10,744	$ 10,208	$ 11,503	$ 11,010	$ 46,481	$ 43,465	$ 40,824
Weighted average common shares outstanding - basic	17,142	17,090	17,067	17,023	17,004	16,939	16,811	16,759	17,081	16,879	16,689
Weighted average common shares outstanding - diluted	17,245	17,203	17,194	17,157	17,167	17,102	16,989	16,939	17,208	17,067	16,872
Basic earnings per common share (in dollars per share)	$ 0.71	$ 0.72	$ 0.65	$ 0.64	$ 0.63	$ 0.60	$ 0.68	$ 0.65	$ 2.72	$ 2.57	$ 2.44
Diluted earnings per common share (in dollars per share)	0.70	0.72	0.64	0.64	0.62	0.60	0.68	0.65	2.70	2.54	2.41
Cash dividends declared per share (in dollars per share)	$ 0.37	$ 0.37	$ 0.36	$ 0.36	$ 0.34	$ 0.34	$ 0.34	$ 0.34	$ 1.46	$ 1.36	$ 1.22