Reclassifications of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized capital gains	$ (29,202)	$ (59,368)	$ (158,513)	$ (197,728)
Other than temporary impairment losses	52,680	720	112,278	6,872
Income taxes	36,045	79,547	138,113	196,415
Net earnings	(97,098)	(186,340)	(405,665)	(540,215)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Appreciation of Investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized capital gains	(29,200)	(59,400)	(158,500)	(197,700)
Other than temporary impairment losses	52,700	700	112,300	6,900
Income taxes	(8,200)	20,600	16,200	66,700
Net earnings	$ 15,300	$ (38,100)	$ (30,000)	$ (124,100)