Financial Instruments (Fair Values of Outstanding Derivative Instruments) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Derivative Assets:
Derivative Assets	$ 791	$ 852
Derivative Liabilities:
Derivative Liabilities	10	4
Level 2 | Foreign exchange contracts | Prepaid revenue share, expenses and other assets, current and non-current
Derivative Assets:
Derivative Assets	791	851
Level 2 | Foreign exchange contracts | Accrued expenses and other current liabilities
Derivative Liabilities:
Derivative Liabilities	9	3
Level 2 | Interest rate contracts | Prepaid revenue share, expenses and other assets, current and non-current
Derivative Assets:
Derivative Assets		1
Level 2 | Interest rate contracts | Accrued expenses and other liabilities, current and non-current
Derivative Liabilities:
Derivative Liabilities	1	1
Fair Value of Derivatives Designated as Hedging Instruments
Derivative Assets:
Derivative Assets	791	852
Derivative Liabilities:
Derivative Liabilities	9	1
Fair Value of Derivatives Designated as Hedging Instruments | Level 2 | Foreign exchange contracts | Prepaid revenue share, expenses and other assets, current and non-current
Derivative Assets:
Derivative Assets	791	851
Fair Value of Derivatives Designated as Hedging Instruments | Level 2 | Foreign exchange contracts | Accrued expenses and other current liabilities
Derivative Liabilities:
Derivative Liabilities	8	0
Fair Value of Derivatives Designated as Hedging Instruments | Level 2 | Interest rate contracts | Prepaid revenue share, expenses and other assets, current and non-current
Derivative Assets:
Derivative Assets		1
Fair Value of Derivatives Designated as Hedging Instruments | Level 2 | Interest rate contracts | Accrued expenses and other liabilities, current and non-current
Derivative Liabilities:
Derivative Liabilities	1	1
Derivatives Not Designated as Hedging Instruments
Derivative Assets:
Derivative Assets	0	0
Derivative Liabilities:
Derivative Liabilities	1	3
Derivatives Not Designated as Hedging Instruments | Level 2 | Foreign exchange contracts | Prepaid revenue share, expenses and other assets, current and non-current
Derivative Assets:
Derivative Assets	0	0
Derivatives Not Designated as Hedging Instruments | Level 2 | Foreign exchange contracts | Accrued expenses and other current liabilities
Derivative Liabilities:
Derivative Liabilities	1	3
Derivatives Not Designated as Hedging Instruments | Level 2 | Interest rate contracts | Prepaid revenue share, expenses and other assets, current and non-current
Derivative Assets:
Derivative Assets		0
Derivatives Not Designated as Hedging Instruments | Level 2 | Interest rate contracts | Accrued expenses and other liabilities, current and non-current
Derivative Liabilities:
Derivative Liabilities	$ 0	$ 0