Reclassifications 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
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains	$ (86,160)	$ (41,524)	$ (129,311)	$ (138,360)
Other than temporary impairment losses	7,317	932	59,598	6,152
Income taxes	61,905	53,186	102,068	116,868
Net earnings	(183,147)	(149,234)	(308,567)	(353,875)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Appreciation of Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized capital gains	(86,200)	(41,500)	(129,300)	(138,400)
Other than temporary impairment losses	7,300	900	59,600	6,200
Income taxes	27,600	14,200	24,400	46,300
Net earnings	$ (51,300)	$ (26,400)	$ (45,300)	$ (85,900)