Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Unrealized Gains (Losses) on Investments arising during the period, Deferred Tax	$ 14,380	$ (8,748)	$ 3,730
Reclassification adjustment for Net Realized (Gains) Losses included in Net Income, Deferred Tax	1,029	5,335	(846)
Non Credit Other-Than-Temporary Impairments arising during the period, Deferred Tax	34	(16)	27
Reclassification Adjustment for Other-Than-Temporary Impairment Credit Losses Recognized in Net Income, Deferred Tax	0	0	0
Change in Foreign Currency Translation Gains (Losses), Deferred Tax	2,069	$ (2,874)	$ 5,017
Change in Benefit Plans' Obligations, Deferred Tax	$ 68