Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net realized investment gains (losses)	$ 8,430	$ 39,918	$ 5,800	$ 39,130
Other than temporary impairment losses on investments	(1,898)	(37)	(2,238)	(62)
Income before income taxes	9,772	44,798	13,010	51,772
Income tax expense (benefit)	1,345	(11,590)	4,901	(9,741)
Net income	11,117	33,208	17,911	42,031
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(917)	(29,756)	(2,716)	(33,788)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains and Losses on Available for Sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net realized investment gains (losses)	(3,745)	(45,840)	(7,126)	(51,374)
Other than temporary impairment losses on investments	1,897	37	2,238	62
Income before income taxes	(1,848)	(45,803)	(4,888)	(51,312)
Income tax expense (benefit)	688	16,109	1,846	17,599
Net income	(1,160)	(29,694)	(3,042)	(33,713)
Reclassification out of Accumulated Other Comprehensive Income | Foreign Currency Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net realized investment gains (losses)	373	(96)	501	(116)
Income tax expense (benefit)	(130)	34	(175)	41
Net income	$ 243	$ (62)	$ 326	$ (75)