Reclassifications of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized capital gains	$ (35,893)	$ (43,151)
Other than temporary impairment losses	20,759	52,281
Income taxes	57,668	40,163
Net earnings	(154,653)	(125,420)
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	(35,900)	(43,100)
Other than temporary impairment losses	20,800	52,300
Income taxes	5,300	(3,300)
Net earnings	$ (9,800)	$ 5,900