Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net Income (Loss)	$ (27,979)	$ 22,013	$ 13,633	$ 61,135
Change in Net Unrealized Gains (Losses) on Investments:
Unrealized Gains (Losses) on Investments arising during the period, net of Deferred Tax	9,653	(2,414)	36,928	43,362
Reclassification adjustment for Net Realized Gains included in Net Income net of Deferred Tax	(1,636)	(519)	134	1,449
Change in Net Unrealized Gains (Losses) on Investments	8,017	(2,933)	37,062	44,811
Change in Other-Than-Temporary Impairments
Non Credit Other-Than-Temporary Impairments arising during the period, net of Deferred Tax	9	15	39	(64)
Reclassification Adjustment for Other-Than-Temporary Impairment Credit Losses Recognized in Net Income net of Deferred Tax	358	0	761	0
Change in Other-Than-Temporary Impairments	367	15	800	(64)
Change in Foreign Currency Translation Gains (Losses), net of Deferred Tax	1,284	(335)	1,803	(6,174)
Other Comprehensive Income (Loss)	9,668	(3,253)	39,665	38,573
Comprehensive Income (Loss)	$ (18,311)	$ 18,760	$ 53,298	$ 99,708