QUARTERLY FINANCIAL INFORMATION (Unaudited) (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	$ 44,243	$ 42,857	$ 41,803	$ 41,653	$ 41,074	$ 40,317	$ 38,849	$ 38,072	$ 170,556	$ 158,312	$ 148,366
Interest expense	5,276	5,126	5,071	5,531	5,297	5,201	4,916	4,699	21,004	20,113	18,818
Net interest income	38,967	37,731	36,732	36,122	35,777	35,116	33,933	33,373	149,552	138,199	129,548
Provision (credit)	572	781	2,957	1,236	1,850	1,706	1,218	597	5,546	5,371	(163)
Non-interest income	12,344	12,584	12,751	13,363	12,243	12,390	12,109	13,159	51,042	49,901	46,871
Non-interest Expense	30,544	29,326	30,871	32,317	26,996	29,630	29,477	29,244	123,058	115,347	120,800
Income before income taxes	20,195	20,208	15,655	15,932	19,174	16,170	15,347	16,691	71,990	67,382	55,782
Income tax expense	6,879	6,734	5,008	5,119	6,372	5,175	5,014	5,466	23,740	22,027	17,582
Net income	$ 13,316	$ 13,474	$ 10,647	$ 10,813	$ 12,802	$ 10,995	$ 10,333	$ 11,225	$ 48,250	$ 45,355	$ 38,200
Earnings Per Share, Basic, Total	$ 0.55	$ 0.56	$ 0.45	$ 0.45	$ 0.53	$ 0.45	$ 0.42	$ 0.45	$ 2	$ 1.84	$ 1.53
Earnings Per Share, Diluted, Total	$ 0.55	$ 0.56	$ 0.44	$ 0.45	$ 0.52	$ 0.45	$ 0.42	$ 0.45	$ 2	$ 1.84	$ 1.52