SCHEDULE I-SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) $ in Thousands	Dec. 31, 2017 USD ($)
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	$ 1,896,443
Fair Value	2,140,790
Amount at which shown in the balance sheet	2,140,790
Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	1,646,411
Fair Value	1,672,239
Amount at which shown in the balance sheet	1,672,239
Debt securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	1,646,411
Fair Value	1,672,239
Amount at which shown in the balance sheet	1,672,239
U.S. government \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	92,561
Fair Value	91,689
Amount at which shown in the balance sheet	91,689
U.S. Agency \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	18,541
Fair Value	18,778
Amount at which shown in the balance sheet	18,778
Non-U.S. govt. & agency \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	7,501
Fair Value	7,588
Amount at which shown in the balance sheet	7,588
Mtge/ABS/CMBS \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	329,129
Fair Value	328,471
Amount at which shown in the balance sheet	328,471
ABS/CMBS \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	70,405
Fair Value	70,526
Amount at which shown in the balance sheet	70,526
Corporate Debt \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	508,128
Fair Value	519,022
Amount at which shown in the balance sheet	519,022
Municipal \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	620,146
Fair Value	636,165
Amount at which shown in the balance sheet	636,165
Equity securities \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	182,002
Fair Value	400,492
Amount at which shown in the balance sheet	400,492
Ind Misc & all other \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	108,815
Fair Value	256,360
Amount at which shown in the balance sheet	256,360
ETFs (Ind/misc) \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	73,187
Fair Value	144,132
Amount at which shown in the balance sheet	144,132
Cash and Short-term Investments \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	34,251
Fair Value	34,251
Amount at which shown in the balance sheet	34,251
Other Invested Assets \| Available for sale securities
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES
Cost	33,779
Fair Value	33,808
Amount at which shown in the balance sheet	$ 33,808

This element represents the carrying (reported) amount of the entity's investments as of the balance sheet date. This amount may represent the individual investment's or group of similar investments' original cost, fair value, or such other amount at which the investment is shown in the entity's balance sheet.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 7
-Subparagraph (SX 210.12-15)
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611379-123010

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