PARENT COMPANY FINANCIAL INFORMATION (Statements of Income) (Detail) - USD ($) $ 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
Income:
Other income									$ 5,312	$ 5,521	$ 4,219
Expenses:
Total interest expense	$ 5,276	$ 5,126	$ 5,071	$ 5,531	$ 5,297	$ 5,201	$ 4,916	$ 4,699	21,004	20,113	18,818
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 (Benefit)	(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
Parent Company [Member]
Income:
Cash dividends from subsidiary									43,975	42,580	19,530
Other income									2,476	995	902
Total income									46,451	43,575	20,432
Expenses:
Interest									944	899	881
Other expenses									1,139	1,123	1,060
Total interest expense									2,083	2,022	1,941
Income before income taxes									44,368	41,553	18,491
Income Tax Expense (Benefit)									78	(308)	(266)
Income before equity in undistributed income of subsidiary									44,290	41,861	18,757
Equity in undistributed income of subsidiary									3,960	3,494	19,443
Net income									$ 48,250	$ 45,355	$ 38,200