Goodwill and Intangible Assets Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended			9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Customer Lists and User Base	Dec. 31, 2012 Customer Lists and User Base	Sep. 30, 2013 Trademarks and Trade Names	Dec. 31, 2012 Trademarks and Trade Names	Sep. 30, 2013 Developed Technology	Dec. 31, 2012 Developed Technology	Sep. 30, 2013 All Other	Dec. 31, 2012 All Other
Intangible Assets:
Gross Carrying Amount	$ 3,220		$ 3,220		$ 3,164	$ 1,648	$ 1,644	$ 771	$ 743	$ 538	$ 525	$ 263	$ 252
Accumulated Amortization	(2,357)		(2,357)		(2,036)	(1,159)	(991)	(645)	(569)	(378)	(322)	(175)	(154)
Weighted-Average Useful Life (Years)						5 years	5 years	5 years	5 years	4 years	4 years	4 years	4 years
Amortization expense	107	110	323	329
Amortization Expense, Fiscal Year Maturity [Abstract]
Remaining 2013	100		100
2014	315		315
2015	252		252
2016	128		128
2017	38		38
Thereafter	30		30
Net Carrying Amount	$ 863		$ 863		$ 1,128	$ 489	$ 653	$ 126	$ 174	$ 160	$ 203	$ 88	$ 98