Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Termination Benefits [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at January 1		$ 49	$ 14	$ 30
Additions (reductions) charged to expense		342	53	(6)
Payments		(83)	(18)	(10)
Balance at December 31		308	49	14
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at January 1		194	95	155
Additions (reductions) charged to expense		251	119	1
Bad debt write-offs		(16)	(20)	(61)
Balance at December 31		429	194	95
Deferred Income Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at January 1	[1]	16,292	17,171	15,443
Additions to deferred income tax expense	[1]	1,440	1,192	2,665
Reduction of deferred income tax expense	[1]	(2,320)	(2,071)	(937)
Balance at December 31	[1]	$ 15,412	$ 16,292	$ 17,171

[1] See also Note 18 to the Consolidated Financial Statements, beginning on page FS-45.