PARENT COMPANY FINANCIAL INFORMATION (Statements of Cash Flows) (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
Cash Flows from Operating Activities:
Net income	$ 13,316	$ 13,474	$ 10,647	$ 10,813	$ 12,802	$ 10,995	$ 10,333	$ 11,225	$ 48,250	$ 45,355	$ 38,200
Adjustments to reconcile net income to net cash provided by operating activities:
Share based compensation expense									2,139	1,979	1,452
Net change in other liabilities									(2,932)	(6,267)	20,166
Other-net									(1,873)	4,628	(4,997)
Net cash provided by operating activities									90,375	50,830	53,664
Cash Flows from Investing Activities:
Purchase of investment available-for-sale									(287,211)	(46,190)	0
Acquistion of business activity, net of cash acquired									(1,347)	0	0
Net cash used in investing activities									(422,993)	(291,915)	(262,337)
Cash Flows from Financing Activities:
Retirement of subordinated debt									(5,000)	0	0
Redemption of stock warrant									(13,273)	(22,624)	(910)
Proceeds from issuance of common stock									897	487	394
Tax benefit from stock options exercised									125	350	321
Repurchase of common stock									(13,273)	(22,624)	(910)
Dividends paid									(23,676)	(22,397)	(19,216)
Net cash provided by financing activities									393,861	217,750	230,463
Net increase (decrease) in cash and cash equivalents									61,243	(23,335)	21,790
Cash and cash equivalents at beginning of period				72,882				96,217	72,882	96,217	74,427
Cash and cash equivalents at end of period	134,125				72,882				134,125	72,882	96,217
Parent Company [Member]
Cash Flows from Operating Activities:
Net income									48,250	45,355	38,200
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed income-subsidiary									(3,960)	(3,494)	(19,443)
Share based compensation expense									2,139	1,979	1,452
Other-net									3,213	10	(261)
Net cash provided by operating activities									49,642	43,850	19,948
Cash Flows from Investing Activities:
Purchase of investment available-for-sale									(7,000)	(2,600)	0
Net cash used in investing activities									(7,000)	(2,600)	0
Cash Flows from Financing Activities:
Retirement of subordinated debt									(5,000)	0	0
Proceeds from issuance of common stock									897	487	394
Tax benefit from stock options exercised									125	350	321
Repurchase of common stock									(13,273)	(22,624)	(910)
Dividends paid									(23,676)	(22,397)	(19,216)
Net cash provided by financing activities									(40,927)	(44,184)	(19,411)
Net increase (decrease) in cash and cash equivalents									1,715	(2,934)	537
Cash and cash equivalents at beginning of period				$ 9,154				$ 12,088	9,154	12,088	11,551
Cash and cash equivalents at end of period	$ 10,869				$ 9,154				$ 10,869	$ 9,154	$ 12,088