SECURITIES - Contractual Maturities of Securities Available for Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Available for Sale, Amortized Cost
Within one year	$ 11,347
One through five years	70,884
Six through ten years	112,190
After ten years	151,795
Amortized Cost, Equity securities	6,233
Amortized Cost	991,538	$ 905,857
Available for Sale, Fair Value
Within one year	11,456
One through five years	74,840
Six through ten years	119,436
After ten years	161,000
Equity securities	6,233
Fair Value	1,025,048	925,279
Mortgage-backed securities-residential (Government Sponsored Entity)
Available for Sale, Amortized Cost
Debt securities without single maturity date	446,989
Amortized Cost	446,989	332,525
Available for Sale, Fair Value
Debt securities without single maturity date	456,464
Fair Value	456,464	334,080
Collateralized mortgage obligations (Government Sponsored Entity)
Available for Sale, Amortized Cost
Debt securities without single maturity date	192,100
Amortized Cost	192,100	228,621
Available for Sale, Fair Value
Debt securities without single maturity date	195,619
Fair Value	$ 195,619	$ 228,749