Shareholders' Equity - Accumulated Other Comprehensive Loss, Net of Tax (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 86,728
Other comprehensive income/(loss) adjustments, net of tax	$ (31)	$ (3)	(169)	$ (168)
Ending Balance	87,110		87,110		$ 86,728
Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(587)	(473)	(473)
Other comprehensive income/(loss) adjustments, net of tax			(58)		(114)
Ending Balance	(645)		(645)		(587)
Debt Valuation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss) adjustments, net of tax			(75)
Ending Balance	230		230
Debt Valuation Adjustment [Member] | Accounting Standards Update 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			305
Ending Balance					305
Pension and Postretirement Liabilities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(131)	(270)	(270)
Other comprehensive income/(loss) adjustments, net of tax			(36)		139
Ending Balance	(167)		(167)		(131)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(718)	$ (743)	(743)
Other comprehensive income/(loss) adjustments, net of tax			(169)		25
Ending Balance	$ (582)		(582)		(718)
Accumulated Other Comprehensive Loss [Member] | Accounting Standards Update 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ (413)
Ending Balance					$ (413)