INVESTMENTS - Fixed Income Securities By Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Amortized cost of available-for-sale debt securities by contractual maturity
Due in one year or less	$ 9,529
Due after one year through five years	275,198
Due after five years through 10 years	565,477
Due after 10 years	326,333
Total amoritzed cost	1,518,156	$ 1,448,204
Fair value of available-for-sale debt securities by contractual maturity
Due in one year or less	9,643
Due after one year through five years	276,100
Due after five years through 10 years	572,675
Due after 10 years	332,852
Total fair value	1,538,110	1,495,087
Net unrealized appreciation of available-for-sale fixed maturities and equity securities	192,900	$ 264,000
Mtge/ABS/CMBS
Amortized cost of available-for-sale debt securities by contractual maturity
Total amoritzed cost	341,619
Fair value of available-for-sale debt securities by contractual maturity
Total fair value	$ 346,840