Income Taxes - Reconciliation of Tax of Income Before Income Taxes and Total Tax Expense (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]
Income tax expense at U.S. statutory rate	$ 1,707	$ 2,833	$ 1,822
State income tax, less federal benefit	6	12	6
Taxes related to foreign operations	773	568	245
Tax credits	(4)	(15)	(8)
Non-deductible merger costs			6
Current and deferred taxes related to currency fluctuations	16	(66)	111
Increase in U.K. tax rate	118	218
Net change in tax contingencies	(115)	(6)	(2)
Increase in valuation allowance	355	8	12
All other, net	20	(43)	(18)
Total	$ 2,876	$ 3,509	$ 2,174