Fair Value Measurements and Financial Instruments - Schedule of assets and liabilities that are measured at fair value on a recurring basis (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Money market funds and highly liquid debt securities [Member] | Recurring [Member]
Assets:
Money market funds and highly liquid debt securities	$ 1,396	$ 1,850
Corporate bonds [Member] | Recurring [Member]
Assets:
Other investments	0	1
Government bonds [Member] | Recurring [Member]
Assets:
Other investments	1	6
Equity securities [Member] | Recurring [Member]
Assets:
Other investments	10	11
Interest rate contracts [Member] | Recurring [Member]
Assets:
Derivative Asset	0	0
Foreign exchange contracts [Member] | Recurring [Member]
Assets:
Derivative Asset	32	46
Liabilities:
Derivatives	18	58
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds and highly liquid debt securities [Member] | Recurring [Member]
Assets:
Money market funds and highly liquid debt securities	1,396	1,850
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds [Member] | Recurring [Member]
Assets:
Other investments	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Government bonds [Member] | Recurring [Member]
Assets:
Other investments	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities [Member] | Recurring [Member]
Assets:
Other investments	6	6
Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate contracts [Member] | Recurring [Member]
Assets:
Derivative Asset	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign exchange contracts [Member] | Recurring [Member]
Assets:
Derivative Asset	0	0
Liabilities:
Derivatives	0	0
Significant Other Observable Inputs (Level 2) | Money market funds and highly liquid debt securities [Member] | Recurring [Member]
Assets:
Money market funds and highly liquid debt securities	0	0
Significant Other Observable Inputs (Level 2) | Corporate bonds [Member] | Recurring [Member]
Assets:
Other investments	0	0
Significant Other Observable Inputs (Level 2) | Government bonds [Member] | Recurring [Member]
Assets:
Other investments	1	6
Significant Other Observable Inputs (Level 2) | Equity securities [Member] | Recurring [Member]
Assets:
Other investments	4	5
Significant Other Observable Inputs (Level 2) | Interest rate contracts [Member] | Recurring [Member]
Assets:
Derivative Asset	0	0
Significant Other Observable Inputs (Level 2) | Foreign exchange contracts [Member] | Recurring [Member]
Assets:
Derivative Asset		46
Liabilities:
Derivatives		58
Significant Unobservable Inputs (Level 3) | Money market funds and highly liquid debt securities [Member] | Recurring [Member]
Assets:
Money market funds and highly liquid debt securities	0	0
Significant Unobservable Inputs (Level 3) | Corporate bonds [Member] | Recurring [Member]
Assets:
Other investments	0	1
Significant Unobservable Inputs (Level 3) | Government bonds [Member] | Recurring [Member]
Assets:
Other investments	0	0
Significant Unobservable Inputs (Level 3) | Equity securities [Member] | Recurring [Member]
Assets:
Other investments	0	0
Significant Unobservable Inputs (Level 3) | Interest rate contracts [Member] | Recurring [Member]
Assets:
Derivative Asset	0	0
Significant Unobservable Inputs (Level 3) | Foreign exchange contracts [Member] | Recurring [Member]
Assets:
Derivative Asset	0	0
Liabilities:
Derivatives	0	0
Foreign exchange contracts [Member] | Designated as Hedging Instrument [Member]
Liabilities:
Derivative Liabilities	$ 18	$ 58