Fair Value Measurement of Assets and Liabilities - Financial Assets and Liabilities Measured at Fair Value, Recurring (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Assets:
Derivatives	$ 90	$ 154
Liabilities:
Derivatives	17
Short-term Investments
Assets:
Investments	6,381	5,333
Long-term Investments
Assets:
Investments	4,624	3,851
Restricted cash | Short-term Investments
Assets:
Investments	21	19
Corporate debt securities | Short-term Investments
Assets:
Investments	6,292	5,246
Corporate debt securities | Long-term Investments
Assets:
Investments	4,624	3,851
Government and agency securities | Short-term Investments
Assets:
Investments	68	68
Recurring
Assets:
Cash and cash equivalents	2,636	1,816
Total financial assets	13,731	11,154
Recurring | Short-term Investments
Assets:
Investments	6,381	5,333
Recurring | Other Current Assets
Assets:
Derivatives	90	154
Recurring | Long-term Investments
Assets:
Investments	4,624	3,851
Recurring | Other Current Liabilities
Liabilities:
Derivatives	59	48
Recurring | Restricted cash | Short-term Investments
Assets:
Investments	21	19
Recurring | Corporate debt securities | Short-term Investments
Assets:
Investments	6,292	5,246
Recurring | Corporate debt securities | Long-term Investments
Assets:
Investments	4,624	3,851
Recurring | Government and agency securities | Short-term Investments
Assets:
Investments	68	68
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	2,636	1,816
Total financial assets	2,657	1,835
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments
Assets:
Investments	21	19
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Current Assets
Assets:
Derivatives	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments
Assets:
Investments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Current Liabilities
Liabilities:
Derivatives	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Restricted cash | Short-term Investments
Assets:
Investments	21	19
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities | Short-term Investments
Assets:
Investments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities | Long-term Investments
Assets:
Investments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government and agency securities | Short-term Investments
Assets:
Investments	0	0
Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	0	0
Total financial assets	11,074	9,319
Recurring | Significant Other Observable Inputs (Level 2) | Short-term Investments
Assets:
Investments	6,360	5,314
Recurring | Significant Other Observable Inputs (Level 2) | Other Current Assets
Assets:
Derivatives	90	154
Recurring | Significant Other Observable Inputs (Level 2) | Long-term Investments
Assets:
Investments	4,624	3,851
Recurring | Significant Other Observable Inputs (Level 2) | Other Current Liabilities
Liabilities:
Derivatives	59	48
Recurring | Significant Other Observable Inputs (Level 2) | Restricted cash | Short-term Investments
Assets:
Investments	0	0
Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities | Short-term Investments
Assets:
Investments	6,292	5,246
Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities | Long-term Investments
Assets:
Investments	4,624	3,851
Recurring | Significant Other Observable Inputs (Level 2) | Government and agency securities | Short-term Investments
Assets:
Investments	$ 68	$ 68