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	Sep. 30, 2019	Dec. 31, 2018
Money market funds and highly liquid debt securities
Assets
Money market funds and highly liquid debt securities	$ 1,851	$ 1,759
Government bonds
Assets
Other investments	1	1
Equity investments
Assets
Other investments	1	2
Gross foreign exchange contracts
Assets
Derivatives	12	21
Liabilities
Derivatives	3	12
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds and highly liquid debt securities
Assets
Money market funds and highly liquid debt securities	1,851	1,759
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	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Gross foreign exchange contracts
Assets
Derivatives	0	0
Liabilities
Derivatives	0	0
Significant Other Observable Inputs (Level 2) | Money market funds and highly liquid debt securities
Assets
Money market funds and highly liquid debt securities	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	1	2
Significant Other Observable Inputs (Level 2) | Gross foreign exchange contracts
Assets
Derivatives	12	21
Liabilities
Derivatives	3	12
Significant Unobservable Inputs (Level 3) | Money market funds and highly liquid debt securities
Assets
Money market funds and highly liquid debt securities	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) | Gross foreign exchange contracts
Assets
Derivatives	0	0
Liabilities
Derivatives	$ 0	$ 0