SECURITIES (Summary of Amortized Costs and Estimated Fair Values of Available-For-Sale Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	$ 805,198	$ 789,229
Available-for-sale, Unrealized Gains	1,510	3,174
Available-for-sale, Unrealized Losses	(9,457)	(12,536)
Available-for-sale securities, at fair value	797,251	779,867
Held-to-maturity securities, at amortized cost	94,207	94,609
Held-to-maturity securities, Unrealized Gains	1,169	618
Held-to-maturity securities, Unrealized Losses	(282)	(631)
Held-to-maturity Securities, Fair Value	95,094	94,596
Obligations of states and political subdivisions
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	7,233	8,848
Available-for-sale, Unrealized Gains	132	153
Available-for-sale, Unrealized Losses	0	0
Available-for-sale securities, at fair value	7,365	9,001
Held-to-maturity securities, at amortized cost	94,207	94,609
Held-to-maturity securities, Unrealized Gains	1,169	618
Held-to-maturity securities, Unrealized Losses	(282)	(631)
Held-to-maturity Securities, Fair Value	95,094	94,596
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	524,763	485,222
Available-for-sale, Unrealized Gains	961	2,515
Available-for-sale, Unrealized Losses	(4,620)	(7,115)
Available-for-sale securities, at fair value	521,104	480,622
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	267,096	289,046
Available-for-sale, Unrealized Gains	131	265
Available-for-sale, Unrealized Losses	(4,837)	(5,421)
Available-for-sale securities, at fair value	262,390	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	168	132
Available-for-sale, Unrealized Losses	0	0
Available-for-sale securities, at fair value	5,651	5,613
Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	804,575	788,597
Available-for-sale, Unrealized Gains	1,392	3,065
Available-for-sale, Unrealized Losses	(9,457)	(12,536)
Available-for-sale securities, at fair value	796,510	779,126
Equity Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	623	632
Available-for-sale, Unrealized Gains	118	109
Available-for-sale, Unrealized Losses	0	0
Available-for-sale securities, at fair value	$ 741	$ 741