Share-Based Compensation - Share-Based Compensation Expense Table (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, pretax	$ 215	$ 197	$ 309
Income tax benefit	78	72	112
Equity Classified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, pretax	132	151	185
Liability Classified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, pretax	83	46	124
Employee and Nonemployee Restricted Stock [Member] | Equity Classified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, pretax	80	103	138
Employee and Nonemployee Stock Options [Member] | Equity Classified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, pretax	51	45	36
Performance Based Share Awards And Other [Member] | Equity Classified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, pretax	1	3	11
Value Creation Plan [Member] | Liability Classified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, pretax	26		104
Performance Based Unit Awards [Member] | Liability Classified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, pretax	28	36	17
Other Performance Based Awards [Member] | Liability Classified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, pretax	28	8
Other Awards [Member] | Liability Classified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, pretax	$ 1	$ 2	$ 3