Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Intangible Assets:
Gross Carrying Amount	$ 1,389		$ 1,389		$ 1,457
Accumulated Amortization	(1,299)		(1,299)		(1,324)
Intangible Assets, Net	90		90		133
Amortization expense	18	$ 19	50	$ 92
Customer lists and user base
Intangible Assets:
Gross Carrying Amount	417		417		434
Accumulated Amortization	(395)		(395)		(407)
Intangible Assets, Net	22		$ 22		$ 27
Weighted Average Useful Life (Years)			5 years		5 years
Marketing related
Intangible Assets:
Gross Carrying Amount	587		$ 587		$ 642
Accumulated Amortization	(561)		(561)		(596)
Intangible Assets, Net	26		$ 26		$ 46
Weighted Average Useful Life (Years)			5 years		5 years
Developed technologies
Intangible Assets:
Gross Carrying Amount	236		$ 236		$ 237
Accumulated Amortization	(211)		(211)		(195)
Intangible Assets, Net	25		$ 25		$ 42
Weighted Average Useful Life (Years)			4 years		4 years
All other
Intangible Assets:
Gross Carrying Amount	149		$ 149		$ 144
Accumulated Amortization	(132)		(132)		(126)
Intangible Assets, Net	$ 17		$ 17		$ 18
Weighted Average Useful Life (Years)			4 years		4 years