Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gains (losses) on investments arising during the period, deferred tax	$ 2,624	$ (14,925)	$ 17,521
Reclassification adjustment for net realized (gains) losses included in net income, deferred tax	9,185	2,776	6,218
Non credit other-than-temporary impairments arising during the period, deferred tax	60	(48)	(174)
Reclassification adjustment for non credit other-than-temporary impairment losses recognized in net income, deferred tax	(90)	0	0
Change in foreign currency translation gains (losses), deferred tax	$ 351	$ 2,800	$ 1,650