INVESTMENTS (Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Available-for-sale Securities, Debt maturities, Amortized cost [Abstract]
One year or less	$ 41,507	$ 24,470
Over one through five years	182,129	170,797
Over five through ten years	145,639	142,728
Over ten years	1,606	26
Amortized cost	370,881	338,021
Available-for-sale Securities, Debt maturities, Fair value [Abstract]
One year or less	41,565	24,488
Over one through five years	185,001	171,113
Over five through ten years	150,694	143,545
Over ten years	1,619	32
Amortized cost	378,879	339,178
Held-to-maturity Securities, Debt maturities, Amortized cost [Abstract]
One year or less	413	486
Over one through five years	1,887	1,899
Over five through ten years	3,580	4,234
Amortized cost	5,880	6,619
Held-to-maturity Securities, Debt Maturities, Fair value [Abstract]
One year or less	413	487
Over one through five years	1,949	1,915
Over five through ten years	3,578	4,037
Estimated fair value	5,940	6,439
Total Investments [Abstract]
Amortized cost	376,761	344,640
Estimated fair value	$ 384,819	$ 345,617