Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 35,040	$ 34,710	$ 33,940	$ 32,414	$ 32,276	$ 32,594	$ 32,775	$ 31,981	$ 136,104	$ 129,626	$ 99,144
Interest expense	5,381	5,550	5,314	4,559	4,032	4,222	4,271	4,029	20,804	16,554	12,692
Net interest income	29,659	29,160	28,626	27,855	28,244	28,372	28,504	27,952	115,300	113,072	86,452
Provision for credit losses	238	817	1,401	579	255	1,279	2,852	872	3,035	5,258	1,936
Non-interest income	9,840	10,299	9,888	8,572	10,151	11,001	10,552	7,917	38,599	39,621	27,482
Non-interest expense	23,099	21,825	22,158	21,428	22,508	22,149	22,330	22,909	88,510	89,896	81,139
Income before income tax expense	16,162	16,817	14,955	14,420	15,632	15,945	13,874	12,088	62,354	57,539	30,859
Income tax expense	19,335	5,478	4,721	4,344	4,730	5,042	4,258	3,442	33,878	17,472	9,907
Net income	$ (3,173)	$ 11,339	$ 10,234	$ 10,076	$ 10,902	$ 10,903	$ 9,616	$ 8,646	$ 28,476	$ 40,067	$ 20,952
Per common share:
Basic earnings per share	$ (0.20)	$ 0.72	$ 0.66	$ 0.65	$ 0.70	$ 0.70	$ 0.62	$ 0.56	$ 1.83	$ 2.59	$ 1.73
Diluted earnings per share	(0.20)	$ 0.72	$ 0.66	$ 0.64	$ 0.70	$ 0.70	$ 0.62	$ 0.56	$ 1.82	$ 2.57	$ 1.73
Change in federal corporate income tax rate									$ 14,263	$ 0	$ 0
Impact of Restatement on Earnings Per Share, Diluted	$ 0.91