Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Intangible Assets:
Gross Carrying Amount	$ 1,434		$ 1,408
Accumulated Amortization	(1,352)		(1,318)
Intangible Assets, Net	82		90
Amortization expense	12	$ 16
Customer lists and user base
Intangible Assets:
Gross Carrying Amount	425		419
Accumulated Amortization	(408)		(399)
Intangible Assets, Net	$ 17		$ 20
Weighted Average Useful Life (Years)	5 years		5 years
Marketing related
Intangible Assets:
Gross Carrying Amount	$ 608		$ 594
Accumulated Amortization	(586)		(570)
Intangible Assets, Net	$ 22		$ 24
Weighted Average Useful Life (Years)	5 years		5 years
Developed technologies
Intangible Assets:
Gross Carrying Amount	$ 244		$ 238
Accumulated Amortization	(221)		(215)
Intangible Assets, Net	$ 23		$ 23
Weighted Average Useful Life (Years)	4 years		4 years
All other
Intangible Assets:
Gross Carrying Amount	$ 157		$ 157
Accumulated Amortization	(137)		(134)
Intangible Assets, Net	$ 20		$ 23
Weighted Average Useful Life (Years)	4 years		4 years