INVESTMENTS, Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale Securities, Debt maturities, Amortized cost [Abstract]
One year or less	$ 24,470	$ 16,346
Over one through five years	170,797	170,286
Over five through ten years	142,728	94,368
Over ten years	26	26
Amortized cost	338,021	281,026
Available-for-sale Securities, Debt maturities, Fair value [Abstract]
One year or less	24,488	16,364
Over one through five years	171,113	171,320
Over five through ten years	143,545	96,382
Over ten years	32	33
Amortized cost	339,178	284,099
Held-to-maturity Securities, Debt maturities, Amortized cost [Abstract]
One year or less	486	432
Over one through five years	1,899	2,947
Over five through ten years	4,234	4,038
Over ten years	0	0
Amortized cost	6,619	7,417
Held-to-maturity Securities, Debt Maturities, Fair value [Abstract]
One year or less	487	433
Over one through five years	1,915	2,953
Over five through ten years	4,037	3,873
Over ten years	0	0
Estimated fair value	6,439	7,259
Total Investments [Abstract]
Amortized cost	344,640	288,443
Estimated fair value	$ 345,617	$ 291,358