Schedule I - Parent Company Financial Information (Condensed Statements of Comprehensive Income) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Net income	$ (30)	[1]	$ 368	$ 420	$ 473	$ 192	$ 426	$ 356	$ 248	$ 1,231	$ 1,222	$ 1,419
Other comprehensive (loss) income:
Change in gross unrealized investment gains/losses										(338)	164	299
Effect of income taxes										124	(60)	(109)
Total change in unrealized investment gains/losses, net of tax										(214)	104	190
Reclassification adjustment for net realized gains included in investment income										(22)	(33)	(11)
Effect of income taxes										8	12	4
Total reclassification adjustment, net of tax										(14)	(21)	(7)
Other comprehensive (loss) income, net of tax										(228)	83	183
Comprehensive income										1,003	1,305	1,602
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net income										1,231	1,222	1,419
Other comprehensive (loss) income:
Change in gross unrealized investment gains/losses										(338)	164	299
Effect of income taxes										124	(60)	(109)
Total change in unrealized investment gains/losses, net of tax										(214)	104	190
Reclassification adjustment for net realized gains included in investment income										(22)	(33)	(11)
Effect of income taxes										8	12	4
Total reclassification adjustment, net of tax										(14)	(21)	(7)
Other comprehensive (loss) income, net of tax										(228)	83	183
Comprehensive income										$ 1,003	$ 1,305	$ 1,602

[1] The sum of quarterly amounts does not equal full year results due to the anti-dilutive impact of a loss in the fourth quarter. The fourth quarter includes an expense of $243 million ($154 million after tax, or $0.99 per diluted common share) for reserve strengthening associated with our closed block of long-term care insurance policies.