SECURITIES (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 927,438	$ 891,276
Gross Unrealized Gains	24,568	16,661
Gross Unrealized (Losses)	(2,343)	(4,645)
Estimated Fair Value	949,663	903,292
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	258,968	257,740
Gross Unrealized Gains	13,848	10,479
Gross Unrealized (Losses)	(30)	(140)
Estimated Fair Value	272,786	268,079
Corporate and Other Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	109,757	77,628
Gross Unrealized Gains	506	55
Gross Unrealized (Losses)	(1,684)	(1,704)
Estimated Fair Value	108,579	75,979
Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	545,428	544,823
Gross Unrealized Gains	10,165	6,127
Gross Unrealized (Losses)	(629)	(2,779)
Estimated Fair Value	554,964	548,171
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,285	11,085
Gross Unrealized Gains	49	0
Gross Unrealized (Losses)	0	(22)
Estimated Fair Value	$ 13,334	$ 11,063