CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (368,969)	$ 513,368	$ 641,631
Other comprehensive income (loss), net of tax:
Unrealized investment gains (losses) arising during the year	205,419	5,072	(266,384)
Adjustment for reclassification of net realized investment (gains) losses and OTTI losses recognized in net income	(33,134)	62,190	144,991
Unrealized investment gains (losses) arising during the year, net of reclassification adjustment	172,285	67,262	(121,393)
Foreign currency translation adjustment	41,938	(638)	(21,498)
Total other comprehensive income (loss), net of tax	214,223	66,624	(142,891)
Comprehensive income (loss)	$ (154,746)	$ 579,992	$ 498,740