SECURITIES - Contractual Maturities of Securities Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Available for Sale, Amortized Cost
Within one year	$ 15,973
One through five years	80,903
Six through ten years	102,654
After ten years	174,675
Equity securities	4,670
Amortized Cost	1,015,996	$ 1,002,803
Available for Sale, Fair Value
Within one year	16,266
One through five years	84,512
Six through ten years	107,190
After ten years	175,654
Equity securities	4,670
Fair Value	1,022,208	1,007,540
Mortgage-backed securities-residential (Government Sponsored Entity)
Available for Sale, Amortized Cost
Debt securities without single maturity date	437,264
Amortized Cost	437,264	450,006
Available for Sale, Fair Value
Debt securities without single maturity date	434,075
Fair Value	434,075	446,630
Collateralized mortgage obligations (Government Sponsored Entity)
Available for Sale, Amortized Cost
Debt securities without single maturity date	199,857
Amortized Cost	199,857	179,314
Available for Sale, Fair Value
Debt securities without single maturity date	199,841
Fair Value	$ 199,841	$ 179,401