Derivative Instruments (Forward Currency Exchange Contracts) (Details) - Foreign Exchange Contract - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Notional Amount	$ 4,036	$ 3,899
Maximum Term (Days)	548 days	548 days
Derivative, Fair Value, Net	$ (2)	$ 27
Other current assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	19	41
Other noncurrent assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	4
Other current liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	(21)	(16)
Other noncurrent liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	(1)	(2)
Designated
Derivative [Line Items]
Notional Amount	1,131	1,058
Derivative, Fair Value, Net	(4)	17
Designated | Other current assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	11	24
Designated | Other noncurrent assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	4
Designated | Other current liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	(15)	(9)
Designated | Other noncurrent liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	(1)	(2)
Non-Designated
Derivative [Line Items]
Notional Amount	2,905	2,841
Derivative, Fair Value, Net	2	10
Non-Designated | Other current assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	8	17
Non-Designated | Other noncurrent assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Non-Designated | Other current liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	(6)	(7)
Non-Designated | Other noncurrent liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 0	$ 0