Financial Instruments (Fair Values of Outstanding Derivative Instruments) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivative Assets:
Derivative Assets	$ 1,269	$ 852
Derivative Liabilities:
Derivative Liabilities	22	4
Level 2 | Foreign exchange contracts | Prepaid revenue share, expenses and other assets, current and non-current
Derivative Assets:
Derivative Assets	1,269	851
Level 2 | Foreign exchange contracts | Accrued expenses and other current liabilities
Derivative Liabilities:
Derivative Liabilities	19	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	3	1
Fair Value of Derivatives Designated as Hedging Instruments
Derivative Assets:
Derivative Assets	1,265	852
Derivative Liabilities:
Derivative Liabilities	19	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	1,265	851
Fair Value of Derivatives Designated as Hedging Instruments | Level 2 | Foreign exchange contracts | Accrued expenses and other current liabilities
Derivative Liabilities:
Derivative Liabilities	17	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	2	1
Derivatives Not Designated as Hedging Instruments
Derivative Assets:
Derivative Assets	4	0
Derivative Liabilities:
Derivative Liabilities	3	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	4	0
Derivatives Not Designated as Hedging Instruments | Level 2 | Foreign exchange contracts | Accrued expenses and other current liabilities
Derivative Liabilities:
Derivative Liabilities	2	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	$ 1	$ 0