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, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Income tax expense (benefit) at U.S. statutory rate	$ (1,017)	$ 1,541	$ 1,694
State income tax, less federal benefit	(27)	29	6
Taxes related to foreign operations	(144)	200	767
Tax credits		6	(4)
Deferred tax on distributed foreign earnings	311	225
Deferred tax on undistributed foreign earnings	1,654
Current and deferred taxes related to currency fluctuations	(56)	(154)	16
Goodwill impairment	483
Change in U.K. tax rate			118
Net change in tax contingencies	(3)	(10)	(115)
Valuation allowances	478	132	341
All other, net	(42)	(45)	30
Provision (benefit) for income taxes	$ 1,637	$ 1,924	$ 2,853