Discontinued Operations Discontinued Operations (Results of Discontinued Operations) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Discontinued Operations and Disposal Groups [Abstract]
Total revenues, less transaction-based expenses									$ 347	$ 76
Compensation and benefits									105	29
Technology and communication									31	6
Professional services									31	6
Rent and occupancy									12	4
Acquisition-related transaction and integration costs									103	22
Selling, general, administrative									16	4
Depreciation and amortization									16	5
Total operating expenses									314	76
Operating income									33	0
Other income, net									5	(4)
Income tax expense									27	46
Income from discontinued operations, net of tax	$ 0	$ (10)	$ 8	$ 13	$ (50)	$ 0	$ 0	$ 0	$ 11	$ (50)	$ 0