Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gains (losses) on investments arising during the period, deferred tax	$ (549)	$ 8,231	$ 9,858	$ 4,951
Reclassification adjustment for net realized (gains) losses included in net income, deferred tax	293	2,581	1,472	3,088
Non credit other-than-temporary impairments arising during the period, deferred tax	8	14	17	55
Reclassification adjustment for non credit other-than-temporary impairment losses recognized in net income, deferred tax	(101)	0	(170)	0
Change in foreign currency translation gains (losses), deferred tax	$ (1)	$ 0	$ 6	$ 2,800