Supplementary Financial Information (unaudited) (Details 2)	3 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010
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)	40.10%	36.20%	39.00%	38.30%	41.30%	38.80%	35.10%	36.40%
Transaction processing (as a percent)	15.90%	16.60%	16.20%	15.30%	15.70%	14.90%	15.20%	14.10%
Occupancy and equipment (as a percent)	11.80%	10.00%	10.60%	10.00%	11.10%	11.10%	9.60%	10.40%
Telecommunications and data processing services (as a percent)	10.70%	9.70%	10.40%	10.00%	10.20%	9.80%	8.40%	9.30%
Other general and administrative (as a percent)	17.50%	15.50%	16.00%	14.80%	16.30%	16.60%	14.10%	19.20%
Goodwill and other asset impairment (as a percent)	3.30%		157.80%				3.50%
Restructuring charges (as a percent)	5.20%		12.40%		1.30%		1.50%	(0.10%)
Acquisition costs (as a percent)			1.80%		1.70%
Interest expense (as a percent)	0.50%	0.40%	0.30%	0.20%	0.10%	0.10%	0.10%	0.20%
Total expenses (as a percent)	104.90%	88.50%	264.50%	88.60%	97.70%	91.30%	87.50%	89.50%
(Loss) income before income tax expense (as a percent)	(4.90%)	11.50%	(164.50%)	11.40%	2.30%	8.70%	12.50%	10.50%
Income tax (benefit) expense (as a percent)	(2.10%)	4.50%	(27.00%)	5.10%	1.00%	4.00%	7.60%	4.80%
Net (loss) income (as a percent)	(2.80%)	7.00%	(137.50%)	6.40%	1.30%	4.70%	4.90%	5.70%