INVESTMENT SECURITIES, Investment Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Mar. 31, 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	150	268
12 months or longer | Position	16	17
Total | Position	166	285
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 396,611	$ 637,887
12 months or longer	21,230	21,790
Total	417,841	659,677
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	3,434	4,840
12 months or longer	863	830
Total	$ 4,297	$ 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	7	13
12 months or longer | Position	0	0
Total | Position	7	13
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 258,008	$ 449,242
12 months or longer	0	0
Total	258,008	449,242
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	1,106	2,118
12 months or longer	0	0
Total	$ 1,106	$ 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	75	197
12 months or longer | Position	0	0
Total | Position	75	197
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 40,177	$ 102,106
12 months or longer	0	0
Total	40,177	102,106
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	446	1,054
12 months or longer	0	0
Total	$ 446	$ 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	67	57
12 months or longer | Position	14	15
Total | Position	81	72
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 95,749	$ 83,862
12 months or longer	21,228	21,788
Total	116,977	105,650
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	1,866	1,637
12 months or longer	863	830
Total	$ 2,729	$ 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	$ 2,677	$ 2,677
12 months or longer	0	0
Total	2,677	2,677
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	16	31
12 months or longer	0	0
Total	$ 16	$ 31
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	0	0
12 months or longer | Position	2	2
Total | Position	2	2
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 0	$ 0
12 months or longer	2	2
Total	2	2
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	0	0
12 months or longer	0	0
Total	$ 0	$ 0