Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gains (losses) on investments arising during the period, deferred tax	$ (12,788)	$ 12,615	$ (24,239)	$ 11,023
Reclassification adjustment for net realized (gains) losses included in net income, deferred tax	178	70	(760)	663
Non credit other-than-temporary impairments arising during the period, deferred tax	4	17	42	10
Reclassification adjustment for non credit other-than-temporary impairment losses recognized in net income, deferred tax	(603)	(143)	(709)	(170)
Change in foreign currency translation gains (losses), deferred tax	$ 2,963	$ (422)	$ 3,146	$ (7)