Fair Value Measurements and Financial Instruments - Schedule of assets and liabilities that are measured at fair value on a recurring basis (Details) - Recurring - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Money market funds
Assets:
Money market funds	$ 1,371	$ 1,396
Government bonds
Assets:
Other investments:	1	1
Equity investments
Assets:
Other investments:	9	10
Foreign exchange contracts
Assets:
Derivatives	15	32
Liabilities:
Derivatives:	14	18
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds
Assets:
Money market funds	1,371	1,396
Quoted Prices in Active Markets for Identical Assets (Level 1) | Government bonds
Assets:
Other investments:	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity investments
Assets:
Other investments:	6	6
Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign exchange contracts
Assets:
Derivatives	0	0
Liabilities:
Derivatives:	0	0
Significant Other Observable Inputs (Level 2) | Money market funds
Assets:
Money market funds	0	0
Significant Other Observable Inputs (Level 2) | Government bonds
Assets:
Other investments:	1	1
Significant Other Observable Inputs (Level 2) | Equity investments
Assets:
Other investments:	3	4
Significant Other Observable Inputs (Level 2) | Foreign exchange contracts
Assets:
Derivatives	15	32
Liabilities:
Derivatives:	14	18
Significant Unobservable Inputs (Level 3) | Money market funds
Assets:
Money market funds	0	0
Significant Unobservable Inputs (Level 3) | Government bonds
Assets:
Other investments:	0	0
Significant Unobservable Inputs (Level 3) | Equity investments
Assets:
Other investments:	0	0
Significant Unobservable Inputs (Level 3) | Foreign exchange contracts
Assets:
Derivatives	0	0
Liabilities:
Derivatives:	$ 0	$ 0