Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands													3 Months Ended								12 Months Ended
	Oct. 24, 2018	Jul. 24, 2018	Apr. 25, 2018	Jan. 24, 2018	Oct. 25, 2017	Jul. 25, 2017	Apr. 25, 2017	Jan. 25, 2017	Oct. 26, 2016	Jul. 20, 2016	Apr. 20, 2016	Jan. 27, 2016	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Interest income													$ 54,865	$ 54,576	$ 46,671	$ 43,247	$ 39,544	$ 37,275	$ 36,041	$ 34,849	$ 199,359	$ 147,709	$ 138,512
Interest expense													3,595	3,480	2,928	2,410	2,389	2,333	1,907	1,717	12,413	8,346	6,006
Net interest income													51,270	51,096	43,743	40,837	37,155	34,942	34,134	33,132	186,946	139,363	132,506
Provision for loan losses													1,162	1,065	1,750	1,152	1,338	884	1,131	867	5,129	4,220	4,931
Net interest income after provision for loan losses													50,108	50,031	41,993	39,685	35,817	34,058	33,003	32,265	181,817	135,143	127,575
Noninterest income													8,464	8,080	7,573	7,548	9,064	8,443	10,709	7,363	31,665	35,579	31,619
Noninterest expense													37,345	39,597	35,706	36,747	27,588	27,955	27,809	27,223	149,395	110,575	106,473
Income before income taxes													21,227	18,514	13,860	10,486	17,293	14,546	15,903	12,405	64,087	60,147	52,721
Income tax expense													4,618	3,010	2,003	1,399	7,270	3,922	4,075	3,089	11,030	18,356	13,803
Net income													$ 16,609	$ 15,504	$ 11,857	$ 9,087	$ 10,023	$ 10,624	$ 11,828	$ 9,316	$ 53,057	$ 41,791	$ 38,918
Basic earnings per common share (in usd per share)													$ 0.45	$ 0.42	$ 0.35	$ 0.27	$ 0.33	$ 0.35	$ 0.40	$ 0.31	$ 1.49	$ 1.39	$ 1.30
Diluted earnings per common share (in usd per share)													0.45	0.42	0.35	0.27	0.33	0.35	0.40	0.31	1.49	1.39	1.30
Cash dividends declared on common stock (in usd per share)	$ 0.17	$ 0.15	$ 0.15	$ 0.15	$ 0.13	$ 0.13	$ 0.13	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.11	$ 0.27	$ 0.15	$ 0.15	$ 0.15	$ 0.23	$ 0.13	$ 0.13	$ 0.12	$ 0.72	$ 0.61	$ 0.72