Fair Value Measurement of Assets and Liabilities - Financial Assets and Liabilities Measured at Fair Value, Recurring and Nonrecurring (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Assets:
Derivatives	$ 190	$ 97
Liabilities:
Derivatives	6
Short-term Investments
Assets:
Investments	5,327	4,299
Long-term Investments
Assets:
Investments	3,240	3,267
Corporate debt securities | Short-term Investments
Assets:
Investments	4,295	3,287
Corporate debt securities | Long-term Investments
Assets:
Investments	3,240	3,267
Equity instruments | Short-term Investments
Assets:
Investments	957	929
Recurring
Assets:
Cash and cash equivalents	2,686	1,832
Total financial assets	11,443	9,495
Recurring | Short-term Investments
Assets:
Investments	5,327	4,299
Recurring | Other Current Assets
Assets:
Derivatives	190	97
Recurring | Long-term Investments
Assets:
Investments	3,240	3,267
Recurring | Other Current Liabilities
Liabilities:
Derivatives	62	25
Recurring | Restricted cash | Short-term Investments
Assets:
Investments	25	28
Recurring | Corporate debt securities | Short-term Investments
Assets:
Investments	4,295	3,287
Recurring | Corporate debt securities | Long-term Investments
Assets:
Investments	3,240	3,267
Recurring | Government and agency securities | Short-term Investments
Assets:
Investments	50	55
Recurring | Equity instruments | Short-term Investments
Assets:
Investments	957	929
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	2,156	1,664
Total financial assets	3,138	2,621
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments
Assets:
Investments	982	957
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	25	28
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 | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity instruments | Short-term Investments
Assets:
Investments	957	929
Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	530	168
Total financial assets	8,305	6,874
Recurring | Significant Other Observable Inputs (Level 2) | Short-term Investments
Assets:
Investments	4,345	3,342
Recurring | Significant Other Observable Inputs (Level 2) | Other Current Assets
Assets:
Derivatives	190	97
Recurring | Significant Other Observable Inputs (Level 2) | Long-term Investments
Assets:
Investments	3,240	3,267
Recurring | Significant Other Observable Inputs (Level 2) | Other Current Liabilities
Liabilities:
Derivatives	62	25
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	4,295	3,287
Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities | Long-term Investments
Assets:
Investments	3,240	3,267
Recurring | Significant Other Observable Inputs (Level 2) | Government and agency securities | Short-term Investments
Assets:
Investments	50	55
Recurring | Significant Other Observable Inputs (Level 2) | Equity instruments | Short-term Investments
Assets:
Investments	$ 0	$ 0