INVESTMENTS - Fixed Income Securities By Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Amortized cost of available-for-sale debt securities by contractual maturity
Due in one year or less	$ 41,319
Due after one year through five years	411,153
Due after five years through 10 years	615,061
Due after 10 years	168,716
Total amortized cost	1,776,465	$ 1,646,411
Fair value of available-for-sale debt securities by contractual maturity
Due in one year or less	41,333
Due after one year through five years	410,680
Due after five years through 10 years	608,115
Due after 10 years	168,412
Total fair value	1,760,515	$ 1,672,239
Mtge/ABS/CMBS
Amortized cost of available-for-sale debt securities by contractual maturity
Total amortized cost	540,216
Fair value of available-for-sale debt securities by contractual maturity
Total fair value	$ 531,975

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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