Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI, beginning balance	$ 4,636
Other comprehensive income	44	$ 138
AOCI, ending balance	4,998
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI, beginning balance	(2,586)	(2,561)
Other comprehensive income (loss) before reclassifications	51	126
Net losses (gains) reclassified from accumulated other comprehensive loss	(7)	12
Other comprehensive income	44	138
AOCI, ending balance	(2,542)	(2,423)
Foreign currency translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI, beginning balance	(1,435)	(1,270)
Other comprehensive income (loss) before reclassifications	170	188
Net losses (gains) reclassified from accumulated other comprehensive loss	0	0
Other comprehensive income	170	188
AOCI, ending balance	(1,265)	(1,082)
Net investment hedging activities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI, beginning balance	140
Other comprehensive income (loss) before reclassifications	(64)
Other comprehensive income	(64)
AOCI, ending balance	76
Pension and post- employment benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI, beginning balance	(1,513)	(1,378)
Other comprehensive income (loss) before reclassifications	(8)	1
Net losses (gains) reclassified from accumulated other comprehensive loss	19	14
Other comprehensive income	11	15
AOCI, ending balance	(1,502)	(1,363)
Marketable security activities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI, beginning balance	46	47
Other comprehensive income (loss) before reclassifications	2	(24)
Net losses (gains) reclassified from accumulated other comprehensive loss	(10)	(1)
Other comprehensive income	(8)	(25)
AOCI, ending balance	38	22
Cash flow hedging activities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI, beginning balance	176	40
Other comprehensive income (loss) before reclassifications	(49)	(39)
Net losses (gains) reclassified from accumulated other comprehensive loss	(16)	(1)
Other comprehensive income	(65)	(40)
AOCI, ending balance	$ 111	$ 0