INVESTMENT SECURITIES, Investment Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Jun. 30, 2017 USD ($) Position	Dec. 31, 2016 USD ($) Position
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	193	268
12 months or longer | Position	19	17
Total | Position	212	285
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 432,470	$ 637,887
12 months or longer	23,079	21,790
Total	455,549	659,677
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	2,259	4,840
12 months or longer	907	830
Total	$ 3,166	$ 5,670
U.S. Treasury and Agency Securities [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	22	13
12 months or longer | Position	0	0
Total | Position	22	13
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 181,119	$ 449,242
12 months or longer	0	0
Total	181,119	449,242
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	181	2,118
12 months or longer	0	0
Total	$ 181	$ 2,118
Obligations of State and Political Subdivisions [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	17	197
12 months or longer | Position	0	0
Total | Position	17	197
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 9,528	$ 102,106
12 months or longer	0	0
Total	9,528	102,106
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	67	1,054
12 months or longer	0	0
Total	$ 67	$ 1,054
Government Agency Mortgage-Backed Securities [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	123	57
12 months or longer | Position	17	15
Total | Position	140	72
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 168,879	$ 83,862
12 months or longer	23,077	21,788
Total	191,956	105,650
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	1,897	1,637
12 months or longer	907	830
Total	$ 2,804	$ 2,467
Corporate Debt Securities [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	1	1
12 months or longer | Position	0	0
Total | Position	1	1
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 2,671	$ 2,677
12 months or longer	0	0
Total	2,671	2,677
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	7	31
12 months or longer	0	0
Total	$ 7	$ 31
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	30	0
12 months or longer | Position	2	2
Total | Position	32	2
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 70,273	$ 0
12 months or longer	2	2
Total	70,275	2
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	107	0
12 months or longer	0	0
Total	$ 107	$ 0