Fair Value Measurement of Assets and Liabilities - Financial Assets and Liabilities Measured at Fair Value, Recurring (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Assets:
Derivatives	$ 107	$ 154
Liabilities:
Derivatives	1
Short-term Investments
Assets:
Investments	4,775	5,333
Long-term Investments
Assets:
Investments	4,421	3,851
Restricted cash | Short-term Investments
Assets:
Investments	20	19
Corporate debt securities | Short-term Investments
Assets:
Investments	4,687	5,246
Corporate debt securities | Long-term Investments
Assets:
Investments	4,421	3,851
Government and agency securities | Short-term Investments
Assets:
Investments	68	68
Recurring
Assets:
Cash and cash equivalents	1,979	1,816
Total financial assets	11,282	11,154
Recurring | Short-term Investments
Assets:
Investments	4,775	5,333
Recurring | Other Current Assets
Assets:
Derivatives	107	154
Recurring | Long-term Investments
Assets:
Investments	4,421	3,851
Recurring | Other Current Liabilities
Liabilities:
Derivatives	33	48
Recurring | Restricted cash | Short-term Investments
Assets:
Investments	20	19
Recurring | Corporate debt securities | Short-term Investments
Assets:
Investments	4,687	5,246
Recurring | Corporate debt securities | Long-term Investments
Assets:
Investments	4,421	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	1,979	1,816
Total financial assets	1,999	1,835
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments
Assets:
Investments	20	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	20	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	9,283	9,319
Recurring | Significant Other Observable Inputs (Level 2) | Short-term Investments
Assets:
Investments	4,755	5,314
Recurring | Significant Other Observable Inputs (Level 2) | Other Current Assets
Assets:
Derivatives	107	154
Recurring | Significant Other Observable Inputs (Level 2) | Long-term Investments
Assets:
Investments	4,421	3,851
Recurring | Significant Other Observable Inputs (Level 2) | Other Current Liabilities
Liabilities:
Derivatives	33	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	4,687	5,246
Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities | Long-term Investments
Assets:
Investments	4,421	3,851
Recurring | Significant Other Observable Inputs (Level 2) | Government and agency securities | Short-term Investments
Assets:
Investments	$ 68	$ 68