Fair Value Measurements - Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	$ 585	$ 417
Gross Amounts of Derivative Assets Presented in the Consolidated Balance Sheet	171	146
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	56	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	152	127
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	24	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	19	19
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	32	31
Fair value on a recurring basis | Corporate debt securities
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	16
Fair value on a recurring basis | Commercial paper
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	510	366
Fair value on a recurring basis | Certificates of deposit/time deposits
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	10	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	152	127
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	24	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	19	19
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	32	31
Fair value on a recurring basis | Level 2 | Corporate debt securities
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	16
Fair value on a recurring basis | Level 2 | Commercial paper
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	510	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	10	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