SECURITIES (Summary of Amortized Costs and Estimated Fair Values of Available-For-Sale Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	$ 817,573	$ 789,229
Available-for-sale, Unrealized Gains	3,508	3,174
Available-for-sale, Unrealized Losses	(10,223)	(12,536)
Available-for-sale securities, at fair value	810,858	779,867
Held-to-maturity securities, at amortized cost	94,340	94,609
Held-to-maturity securities, Unrealized Gains	1,037	618
Held-to-maturity securities, Unrealized Losses	(369)	(631)
Held-to-maturity Securities, Fair Value	95,008	94,596
Obligations of states and political subdivisions
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	7,235	8,848
Available-for-sale, Unrealized Gains	157	153
Available-for-sale, Unrealized Losses	0	0
Available-for-sale securities, at fair value	7,392	9,001
Held-to-maturity securities, at amortized cost	94,340	94,609
Held-to-maturity securities, Unrealized Gains	1,037	618
Held-to-maturity securities, Unrealized Losses	(369)	(631)
Held-to-maturity Securities, Fair Value	95,008	94,596
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	524,635	485,222
Available-for-sale, Unrealized Gains	2,280	2,515
Available-for-sale, Unrealized Losses	(5,239)	(7,115)
Available-for-sale securities, at fair value	521,676	480,622
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	279,588	289,046
Available-for-sale, Unrealized Gains	268	265
Available-for-sale, Unrealized Losses	(4,984)	(5,421)
Available-for-sale securities, at fair value	274,872	283,890
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	5,483	5,481
Available-for-sale, Unrealized Gains	193	132
Available-for-sale, Unrealized Losses	0	0
Available-for-sale securities, at fair value	5,676	5,613
Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	816,941	788,597
Available-for-sale, Unrealized Gains	2,898	3,065
Available-for-sale, Unrealized Losses	(10,223)	(12,536)
Available-for-sale securities, at fair value	809,616	779,126
Equity Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	632	632
Available-for-sale, Unrealized Gains	610	109
Available-for-sale, Unrealized Losses	0	0
Available-for-sale securities, at fair value	$ 1,242	$ 741