Quarterly Financial Summary - Quarterly Financial Summary (Detail) - 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
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 59,692	$ 55,337	$ 51,503	$ 50,046	$ 51,813	$ 44,857	$ 43,055	$ 42,851	$ 216,578	$ 182,576	$ 160,337
Interest expense	6,738	6,316	5,089	4,690	3,917	3,860	3,965	4,034	22,833	15,776	15,830
Net interest income	52,954	49,021	46,414	45,356	47,896	40,997	39,090	38,817	193,745	166,800	144,507
Provision for loan losses	5,124	5,828	1,254	780	1,778	1,453	3,773	786	12,986	7,790	3,580
Net interest income after provision for loan losses	47,830	43,193	45,160	44,576	46,118	39,544	35,317	38,031	180,759	159,010	140,927
Noninterest income	27,587	26,849	24,849	23,070	23,037	21,665	22,458	21,095	102,355	88,255	78,278
Noninterest expenses	48,237	50,497	44,027	43,199	47,187	38,705	38,654	38,913	185,960	163,459	146,645
Income before taxes	27,180	19,545	25,982	24,447	21,968	22,504	19,121	20,213	97,154	83,806	72,560
Income tax provision	9,070	6,823	8,504	8,677	7,984	8,078	6,887	7,324	33,074	30,273	18,803
Net income	$ 18,110	$ 12,722	$ 17,478	$ 15,770	$ 13,984	$ 14,426	$ 12,234	$ 12,889	$ 64,080	$ 53,533	$ 53,757
Earnings per share:
Basic	$ 0.58	$ 0.42	$ 0.59	$ 0.53	$ 0.47	$ 0.52	$ 0.43	$ 0.46	$ 2.12	$ 1.88	$ 1.98
Diluted	$ 0.56	$ 0.41	$ 0.58	$ 0.52	$ 0.46	$ 0.51	$ 0.43	$ 0.45	$ 2.06	$ 1.85	$ 1.93