SECURITIES - Contractual Maturities of Securities Available for Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available for Sale, Amortized Cost
Within one year	$ 16,223
One through five years	85,639
Six through ten years	98,487
After ten years	178,582
Equity securities	4,670
Amortized Cost	1,068,577	$ 1,002,803
Available for Sale, Fair Value
Within one year	16,444
One through five years	89,449
Six through ten years	103,072
After ten years	182,590
Equity securities	4,670
Fair Value	1,079,555	1,007,540
Mortgage-backed securities-residential (Government Sponsored Entity)
Available for Sale, Amortized Cost
Debt securities without single maturity date	465,742
Amortized Cost	465,742	450,006
Available for Sale, Fair Value
Debt securities without single maturity date	463,940
Fair Value	463,940	446,630
Collateralized mortgage obligations (Government Sponsored Entity)
Available for Sale, Amortized Cost
Debt securities without single maturity date	219,234
Amortized Cost	219,234	179,314
Available for Sale, Fair Value
Debt securities without single maturity date	219,390
Fair Value	$ 219,390	$ 179,401