Derivative Instruments (Forward Currency Exchange Contracts) (Details) - Foreign Exchange Contract - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Notional Amount	$ 3,513	$ 4,950
Maximum Term (Days)	546 days	546 days
Derivative, Fair Value, Net	$ (17)	$ 59
Other current assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	12	68
Other noncurrent assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	1
Other current liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	(28)	(9)
Other noncurrent liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	(1)	(1)
Designated
Derivative [Line Items]
Notional Amount	840	889
Derivative, Fair Value, Net	(18)	21
Designated | Other current assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	5	27
Designated | Other noncurrent assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	1
Designated | Other current liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	(22)	(6)
Designated | Other noncurrent liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	(1)	(1)
Non-Designated
Derivative [Line Items]
Notional Amount	2,673	4,061
Derivative, Fair Value, Net	1	38
Non-Designated | Other current assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	7	41
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)	(3)
Non-Designated | Other noncurrent liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 0	$ 0