Income Taxes - Reconciliation of Tax of Income Before Income Taxes and Total Tax Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income tax expense (benefit) at U.S. statutory rate	$ (589)	$ (4,259)	$ (2,391)
State income tax, less federal effect	(19)	(7)	(28)
Taxes related to foreign operations	303	(662)	(147)
Tax credits	(1)	(6)	0
Tax on distributed foreign earnings	80	726	311
Foreign tax credits	(136)	(2,090)	0
Deferred tax on undistributed foreign earnings	(31)	1,903	560
Tax impact of goodwill adjustments	0	82	161
Change in U.K. tax rate	(238)	(414)	0
Net change in tax contingencies	(19)	20	(3)
Canadian USD functional currency election	158	0	0
Valuation allowances	10	3,746	1,021
All other, net	40	(49)	(2)
Total	$ (442)	$ (1,010)	$ (518)