Fair Value Measurements - Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	$ 185	$ 417
Gross Amounts of Derivative Assets Presented in the Consolidated Balance Sheet	140	146
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	85	53
Fair value on a recurring basis | Foreign currency forward/option contracts
Assets and Liabilities Measured on Recurring Basis
Gross Amounts of Derivative Assets Presented in the Consolidated Balance Sheet	119	127
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	26	22
Fair value on a recurring basis | Interest rate swap contracts
Assets and Liabilities Measured on Recurring Basis
Gross Amounts of Derivative Assets Presented in the Consolidated Balance Sheet	21	19
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	59	31
Fair value on a recurring basis | Commercial paper
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	102	366
Fair value on a recurring basis | Certificates of deposit/time deposits
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	34	10
Fair value on a recurring basis | Asset-backed securities
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities		1
Fair value on a recurring basis | U.S. municipal securities
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	49	40
Fair value on a recurring basis | Level 2 | Foreign currency forward/option contracts
Assets and Liabilities Measured on Recurring Basis
Gross Amounts of Derivative Assets Presented in the Consolidated Balance Sheet	119	127
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	26	22
Fair value on a recurring basis | Level 2 | Interest rate swap contracts
Assets and Liabilities Measured on Recurring Basis
Gross Amounts of Derivative Assets Presented in the Consolidated Balance Sheet	21	19
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	59	31
Fair value on a recurring basis | Level 2 | Commercial paper
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	102	366
Fair value on a recurring basis | Level 2 | Certificates of deposit/time deposits
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	34	10
Fair value on a recurring basis | Level 2 | Asset-backed securities
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities		1
Fair value on a recurring basis | Level 3 | U.S. municipal securities
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	$ 49	$ 40