Fair Value Measurements - Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	$ 365	$ 1,103
Gross Amounts of Derivative Assets Presented in the Consolidated Balance Sheet	138	78
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	111	197
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	113	57
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	95	190
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	25	21
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	16	7
Fair value on a recurring basis | Corporate debt securities
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities		14
Fair value on a recurring basis | Commercial paper
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	304	899
Fair value on a recurring basis | Certificates of deposit/time deposits
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	31	76
Fair value on a recurring basis | Asset-backed securities Automobile loan related
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities		16
Fair value on a recurring basis | Asset-backed securities Credit card related
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities		68
Fair value on a recurring basis | U.S. municipal securities
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	30	30
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	113	57
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	95	190
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	25	21
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	16	7
Fair value on a recurring basis | Level 2 | Corporate debt securities
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities		14
Fair value on a recurring basis | Level 2 | Commercial paper
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	304	899
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	31	76
Fair value on a recurring basis | Level 2 | Asset-backed securities Automobile loan related
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities		16
Fair value on a recurring basis | Level 2 | Asset-backed securities Credit card related
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities		68
Fair value on a recurring basis | Level 3 | U.S. municipal securities
Assets and Liabilities Measured on Recurring Basis
Available-for-sale marketable securities	$ 30	$ 30