Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Intangible assets:
Gross Carrying Amount	$ 1,413		$ 1,419
Accumulated Amortization	(1,327)		(1,317)
Intangible Assets, Net	86		102
Amortization expense	16	$ 12
Customer lists and user base
Intangible assets:
Gross Carrying Amount	438		434
Accumulated Amortization	(401)		(393)
Intangible Assets, Net	$ 37		$ 41
Weighted Average Useful Life (Years)	5 years		5 years
Marketing related
Intangible assets:
Gross Carrying Amount	$ 559		$ 568
Accumulated Amortization	(548)		(555)
Intangible Assets, Net	$ 11		$ 13
Weighted Average Useful Life (Years)	5 years		5 years
Developed technologies
Intangible assets:
Gross Carrying Amount	$ 262		$ 263
Accumulated Amortization	(235)		(229)
Intangible Assets, Net	$ 27		$ 34
Weighted Average Useful Life (Years)	3 years		3 years
All other
Intangible assets:
Gross Carrying Amount	$ 154		$ 154
Accumulated Amortization	(143)		(140)
Intangible Assets, Net	$ 11		$ 14
Weighted Average Useful Life (Years)	4 years		4 years