Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 81,057	$ 95,329	$ 63,466
Change in net unrealized gains (losses) on investments:
Unrealized gains (losses) on investments arising during the period, net of deferred tax of $2,534, $14,925 and $17,521 in 2015, 2014 and 2013 respectively	(5,331)	28,252	(32,546)
Reclassification adjustment for net realized (gains) losses included in net income net of deferred tax of $9,185, $2,776 and $6,218 in 2015, 2014 and 2013 respectively	(17,058)	(5,156)	(11,548)
Change in net unrealized gains (losses on investments)	(22,389)	23,096	(44,094)
Change in other-than-temporary impairments:
Non credit other-than-temporary impairments arising during the period, net of deferred tax of $60, $48 and $174 in 2015, 2014 and 2013 respectively	(112)	89	320
Reclassification adjustment for non credit other-than-temporary impairment losses recognized in net income net of deferred tax of $0 in 2015, 2014 and 2013 respectively	168
Change in other-than-temporary impairments	56	89	320
Change in foreign currency translation gains (losses), net of deferred tax of $351, $2,800, and $1,650 in 2015, 2014 and 2013 respectively	(622)	(4,986)	(3,074)
Other comprehensive income (loss)	(22,955)	18,199	(46,848)
Comprehensive income (loss)	$ 58,102	$ 113,528	$ 16,618