Fair Value Measurement of Assets and Liabilities - Financial Assets and Liabilities Measured at Fair Value, Recurring and Nonrecurring (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds receivable and customer accounts	$ 11,352	$ 10,545
Derivative assets	181	219
Derivative liabilities	10
Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	5,583	3,769
Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	5,715	5,552
Corporate debt securities | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	3,737	2,519
Corporate debt securities | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	5,664	5,319
Equity instruments | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	1,151	1,037
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	4,971	6,299
Total financial assets	22,289	20,000
Recurring | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	5,583	3,769
Recurring | Funds Receivable And Customer Accounts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds receivable and customer accounts	5,839	4,161
Recurring | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	5,715	5,552
Recurring | Restricted cash | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	44	29
Recurring | Corporate debt securities | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	3,737	2,519
Recurring | Corporate debt securities | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	5,664	5,319
Recurring | Government and agency securities | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	595	3
Recurring | Government and agency securities | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	51	233
Recurring | Time deposits | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	56	181
Recurring | Equity instruments | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	1,151	1,037
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	3,939	3,888
Total financial assets	5,134	4,954
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	1,195	1,066
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Funds Receivable And Customer Accounts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds receivable and customer accounts	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Restricted cash | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	44	29
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government and agency securities | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government and agency securities | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Time deposits | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity instruments | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	1,151	1,037
Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	1,032	2,411
Total financial assets	17,155	15,046
Recurring | Significant Other Observable Inputs (Level 2) | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	4,388	2,703
Recurring | Significant Other Observable Inputs (Level 2) | Funds Receivable And Customer Accounts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds receivable and customer accounts	5,839	4,161
Recurring | Significant Other Observable Inputs (Level 2) | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	5,715	5,552
Recurring | Significant Other Observable Inputs (Level 2) | Restricted cash | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	3,737	2,519
Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	5,664	5,319
Recurring | Significant Other Observable Inputs (Level 2) | Government and agency securities | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	595	3
Recurring | Significant Other Observable Inputs (Level 2) | Government and agency securities | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	51	233
Recurring | Significant Other Observable Inputs (Level 2) | Time deposits | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	56	181
Recurring | Significant Other Observable Inputs (Level 2) | Equity instruments | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Recurring | Foreign Exchange Contract | Other Current Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	181	219
Recurring | Foreign Exchange Contract | Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	61	27
Recurring | Foreign Exchange Contract | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Current Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Recurring | Foreign Exchange Contract | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0	0
Recurring | Foreign Exchange Contract | Significant Other Observable Inputs (Level 2) | Other Current Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	181	219
Recurring | Foreign Exchange Contract | Significant Other Observable Inputs (Level 2) | Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	$ 61	$ 27