Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - 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]
Unrealized Gains on Investments arising during the period, Deferred Tax	$ (5,197)	$ 1,300	$ (19,884)	$ (23,349)
Reclassification adjustment for Net Realized (Gains) Losses included in Net Income, Deferred Tax	881	279	(72)	(780)
Non Credit Other-Than-Temporary Impairments arising during the period, Deferred Tax	(6)	(8)	(21)	34
Reclassification Adjustment for Other-Than-Temporary Impairment Credit Losses Recognized in Net Income, Deferred Tax	(193)	0	(410)	0
Change in Foreign Currency Translation Gains (Losses), Deferred Tax	$ (691)	$ 175	$ (971)	$ 3,322