Schedule Summarizing Quarterly Operation Results (Detail) (USD $) In Millions, except Per Share data, 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
Quarterly Financial Information [Line Items]
Total revenues	$ 10,187	[1]	$ 10,319	$ 10,321	$ 10,486	$ 9,557	$ 9,651	$ 9,699	$ 10,219	$ 41,313	$ 39,126	$ 36,832
Income (loss) before income taxes	(49)	[1]	586	654	730	282	675	564	390	1,921	1,911	2,235
Net income	$ (30)	[1]	$ 368	$ 420	$ 473	$ 192	$ 426	$ 356	$ 248	$ 1,231	$ 1,222	$ 1,419
Basic earnings (loss) per common share	$ (0.19)	[1]	$ 2.34	$ 2.66	$ 2.97	$ 1.21	$ 2.65	$ 2.19	$ 1.51	$ 7.81	$ 7.56	$ 8.58
Diluted earnings (loss) per common share	$ (0.19)	[1]	$ 2.31	$ 2.63	$ 2.95	$ 1.19	$ 2.62	$ 2.16	$ 1.49	$ 7.73	$ 7.47	$ 8.46

[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.