Fair Value Measurement of Assets and Liabilities - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Assets:
Funds receivable and customer accounts	$ 13,320	$ 12,261
Derivatives	89
Liabilities:
Derivatives	4
Corporate debt securities
Assets:
Funds receivable and customer accounts	991	180
Government and agency securities
Assets:
Funds receivable and customer accounts	5,557	4,305
Time deposits
Assets:
Funds receivable and customer accounts	445	830
Fair value, measurements, recurring basis
Assets:
Cash and cash equivalents	338	406
Funds receivable and customer accounts	7,192	6,978
Derivatives	128	97
Total financial assets	12,666	11,821
Liabilities:
Derivatives	43	25
Fair value, measurements, recurring basis | Short-term investments
Assets:
Investments	3,719	2,018
Fair value, measurements, recurring basis | Short-term investments | Restricted cash
Assets:
Investments	18	18
Fair value, measurements, recurring basis | Short-term investments | Corporate debt securities
Assets:
Investments	3,108	1,998
Fair value, measurements, recurring basis | Short-term investments | Government and agency securities
Assets:
Investments	431
Fair value, measurements, recurring basis | Short-term investments | Time deposits
Assets:
Investments	162	2
Fair value, measurements, recurring basis | Long-term investments
Assets:
Investments	1,289	2,322
Fair value, measurements, recurring basis | Long-term investments | Restricted cash
Assets:
Investments		8
Fair value, measurements, recurring basis | Long-term investments | Corporate debt securities
Assets:
Investments	1,253	2,314
Fair value, measurements, recurring basis | Long-term investments | Government and agency securities
Assets:
Investments	36
Fair value, measurements, recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	0	0
Funds receivable and customer accounts	0	0
Derivatives	0	0
Total financial assets	18	26
Liabilities:
Derivatives	0	0
Fair value, measurements, recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments
Assets:
Investments	18	18
Fair value, measurements, recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Restricted cash
Assets:
Investments	18	18
Fair value, measurements, recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Corporate debt securities
Assets:
Investments	0	0
Fair value, measurements, recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Government and agency securities
Assets:
Investments	0
Fair value, measurements, recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Time deposits
Assets:
Investments	0	0
Fair value, measurements, recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term investments
Assets:
Investments	0	8
Fair value, measurements, recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term investments | Restricted cash
Assets:
Investments		8
Fair value, measurements, recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term investments | Corporate debt securities
Assets:
Investments	0	0
Fair value, measurements, recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term investments | Government and agency securities
Assets:
Investments	0
Fair value, measurements, recurring basis | Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	338	406
Funds receivable and customer accounts	7,192	6,978
Derivatives	128	97
Total financial assets	12,648	11,795
Liabilities:
Derivatives	43	25
Fair value, measurements, recurring basis | Significant Other Observable Inputs (Level 2) | Short-term investments
Assets:
Investments	3,701	2,000
Fair value, measurements, recurring basis | Significant Other Observable Inputs (Level 2) | Short-term investments | Restricted cash
Assets:
Investments	0	0
Fair value, measurements, recurring basis | Significant Other Observable Inputs (Level 2) | Short-term investments | Corporate debt securities
Assets:
Investments	3,108	1,998
Fair value, measurements, recurring basis | Significant Other Observable Inputs (Level 2) | Short-term investments | Government and agency securities
Assets:
Investments	431
Fair value, measurements, recurring basis | Significant Other Observable Inputs (Level 2) | Short-term investments | Time deposits
Assets:
Investments	162	2
Fair value, measurements, recurring basis | Significant Other Observable Inputs (Level 2) | Long-term investments
Assets:
Investments	1,289	2,314
Fair value, measurements, recurring basis | Significant Other Observable Inputs (Level 2) | Long-term investments | Restricted cash
Assets:
Investments		0
Fair value, measurements, recurring basis | Significant Other Observable Inputs (Level 2) | Long-term investments | Corporate debt securities
Assets:
Investments	1,253	$ 2,314
Fair value, measurements, recurring basis | Significant Other Observable Inputs (Level 2) | Long-term investments | Government and agency securities
Assets:
Investments	$ 36