Schedule of Details Supporting Computation of Earnings Per Share (Detail) (USD $) In Millions, except Share data in Thousands, 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
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ (30)	[1]	$ 368	$ 420	$ 473	$ 192	$ 426	$ 356	$ 248	$ 1,231	$ 1,222	$ 1,419
Weighted-average outstanding shares of common stock used to compute basic earnings per common share										157,503	161,484	165,413
Shares used to compute diluted earnings per common share										159,151	163,457	167,827
Basic earnings 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 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
Number of antidilutive stock options and restricted stock awards excluded from computation										704	754	864
Employee Stock Options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock										322	576	959
Restricted Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock										1,326	1,397	1,455

[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.