Consolidated Statements of Comprehensive Income - 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]
Net income	$ 16,190	$ 19,184	$ 39,122	$ 45,113
Change in net unrealized gains (losses) on investments:
Unrealized gains (losses) on investments arising during the period, net of deferred tax	23,751	(23,884)	45,018	(20,929)
Reclassification adjustment for net realized (gains) losses included in net income, net of deferred tax	(331)	(130)	1,411	(1,231)
Change in net unrealized gains (losses) on investments	23,420	(24,014)	46,429	(22,160)
Change in other-than-temporary impairments:
Non credit other-than-temporary impairments arising during the period, net of deferred tax	(8)	(32)	(79)	(17)
Reclassification adjustment for other-than-temporary impairment credit losses recognized in net income, net of deferred tax	1,119	266	1,316	316
Change in other-than-temporary impairments	1,111	234	1,237	299
Change in foreign currency translation gains (losses), net of deferred tax	(5,493)	807	(5,840)	11
Other comprehensive income (loss)	19,038	(22,973)	41,826	(21,850)
Comprehensive income (loss)	$ 35,228	$ (3,789)	$ 80,948	$ 23,263