Summarized Quarterly Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ 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
Summarized Quarterly Information (Unaudited) [Abstract]
Total interest income	$ 29,350	$ 28,730	$ 28,921	$ 28,443	$ 28,430	$ 28,178	$ 27,566	$ 24,159
Total interest expense	2,683	2,607	2,613	2,676	2,566	2,642	2,773	2,740	$ 10,579	$ 10,721	$ 10,694
Net interest income	26,667	26,123	26,308	25,767	25,864	25,536	24,793	21,419	104,865	97,612	69,506
Provision for loan losses	711	1,146	727	955	7,238	5,837	672	350
Net loss on asset disposals and other transactions	(109)	(224)	(769)	(31)	(498)	(51)	(136)	(1,103)	(1,133)	(1,788)	(431)
Net gain on securities transactions	68	(1)	767	96	56	62	11	600	930	729	398
Other income	12,111	13,538	12,367	13,054	12,101	11,906	11,926	11,508
Amortization of other intangible assets	1,007	1,008	1,007	1,008	1,133	1,127	1,144	673	4,030	4,077	1,428
System conversion expenses	746	423	90	0	838	109	732	9,043
Other expense	25,529	25,411	25,408	25,274	25,306	24,876	26,902	23,198
Applicable income tax benefit	3,336	3,656	3,479	3,654	425	1,370	2,231	(151)	14,125	3,875	7,494
Net income	$ 7,408	$ 7,792	$ 7,962	$ 7,995	$ 2,583	$ 4,134	$ 4,913	$ (689)	$ 31,157	$ 10,941	$ 16,684
Earnings per common share - basic	$ 0.41	$ 0.43	$ 0.44	$ 0.44	$ 0.14	$ 0.23	$ 0.27	$ (0.04)	$ 1.72	$ 0.62	$ 1.36
Earnings per common share - diluted	$ 0.41	$ 0.43	$ 0.44	$ 0.44	$ 0.14	$ 0.22	$ 0.27	$ (0.04)	$ 1.71	$ 0.61	$ 1.35
Weighted-average number of common shares outstanding - basic	18,009,056	17,993,443	17,980,797	18,071,746	18,142,997	18,127,131	18,116,090	15,802,334	18,013,693	17,555,140	12,183,352
Weighted-average number of common shares outstanding - diluted	18,172,030	18,110,710	18,113,812	18,194,990	18,278,272	18,271,979	18,253,918	15,930,235	18,155,463	17,687,795	12,306,224