Investments - Unrealized Gain (Loss) on Investments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investment Securities [Line Items]
Total unrealized investment gains (losses)	$ (1,183,652)	$ 614,854	$ 856,692
Equity Securities [Member]
Investment Securities [Line Items]
Total unrealized investment gains (losses)	317	(1,489)	(98)
Fixed Maturities [Member]
Investment Securities [Line Items]
Total unrealized investment gains (losses)	(1,187,529)	613,826	856,424
Securities [Member]
Investment Securities [Line Items]
Total unrealized investment gains (losses)	(1,187,212)	612,337	856,326
Other Investments [Member]
Investment Securities [Line Items]
Total unrealized investment gains (losses)	$ 3,560	$ 2,517	$ 366