Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Unrealized Gains (Losses) on Investments arising during the period, Deferred Tax	$ (12,167)	$ 9,623
Reclassification adjustment for Net Realized (Gains) Losses included in Net Income, Deferred Tax	(50)	509
Non Credit Other-Than-Temporary Impairments arising during the period, Deferred Tax	4	9
Reclassification Adjustment for Other-Than-Temporary Impairment Credit Losses Recognized in Net Income, Deferred Tax	0	0
Change in Foreign Currency Translation Gains (Losses), Deferred Tax	$ 120	$ (1,082)