Supplementary Financial Information (unaudited) (Details 2)	3 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011
Supplementary Financial Information (unaudited)
Total revenues (as a percent)	100.00%	100.00%	100.00%	100.00%	100.00%	100.00%	100.00%	100.00%
Expenses (as a percent)
Compensation and employee benefits (as a percent)	38.80%	39.40%	39.00%	38.60%	40.10%	36.20%	39.00%	38.30%
Transaction processing (as a percent)	16.40%	16.20%	15.50%	16.30%	15.90%	16.60%	16.20%	15.30%
Occupancy and equipment (as a percent)	13.90%	13.40%	11.90%	10.70%	11.80%	10.00%	10.60%	10.00%
Telecommunications and data processing services (as a percent)	12.40%	12.60%	11.60%	11.00%	10.70%	9.70%	10.40%	10.00%
Other general and administrative (as a percent)	17.30%	17.70%	18.60%	16.60%	17.50%	15.50%	16.00%	14.80%
Goodwill and other asset impairment (as a percent)			216.10%		3.30%		157.80%
Restructuring charges (as a percent)	7.80%				5.20%		12.40%
Acquisition - related costs (as a percent)							1.80%
Interest expense (as a percent)	0.50%	0.60%	0.50%	0.50%	0.50%	0.40%	0.30%	0.20%
Total expenses (as a percent)	107.10%	99.80%	313.20%	93.80%	104.90%	88.50%	264.50%	88.60%
(Loss) income before income tax expense (as a percent)	(7.10%)	0.20%	(213.20%)	6.20%	(4.90%)	11.50%	(164.50%)	11.40%
Income tax (benefit) expense (as a percent)	(1.70%)	0.00%	(18.50%)	2.20%	(2.10%)	4.50%	(27.00%)	5.10%
Net (loss) income (as a percent)	(5.30%)	0.20%	(194.70%)	4.00%	(2.80%)	7.00%	(137.50%)	6.40%