Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gains (losses) on investments arising during the period, deferred tax	$ (11,737)	$ (1,723)
Reclassification adjustment for net realized (gains) losses included in net income, deferred tax	(758)	698
Non credit other-than-temporary impairments arising during the period, deferred tax	38	(8)
Reclassification adjustment for non credit other-than-temporary impairment losses recognized in net income, deferred tax	0	0
Change in foreign currency translation gains (losses), deferred tax	$ 183	$ 429