Supplementary Financial Information (unaudited) (Details 2)	3 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012
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)	38.50%	38.90%	36.80%	37.50%	38.80%	39.40%	39.00%	38.60%
Transaction processing (as a percent)	15.10%	15.50%	16.20%	16.30%	16.40%	16.20%	15.50%	16.30%
Occupancy and equipment (as a percent)	12.10%	12.40%	14.90%	12.50%	13.90%	13.40%	11.90%	10.70%
Telecommunications and data processing services (as a percent)	10.00%	9.90%	9.80%	10.70%	12.40%	12.60%	11.60%	11.00%
Other general and administrative (as a percent)	15.60%	14.40%	14.20%	14.20%	17.30%	17.70%	18.60%	16.60%
Goodwill and other asset impairment (as a percent)							216.10%
Restructuring charges (as a percent)			(0.10%)		7.80%
Interest expense (as a percent)	0.60%	0.50%	0.50%	0.50%	0.50%	0.60%	0.50%	0.50%
Total expenses (as a percent)	91.90%	91.60%	92.30%	91.70%	107.10%	99.80%	313.20%	93.80%
Income (loss) before income tax expense (as a percent)	8.10%	8.40%	7.70%	8.30%	(7.10%)	0.20%	(213.20%)	6.20%
Income tax expense (benefit) (as a percent)	0.70%	2.30%	4.10%	1.80%	(1.70%)	0.00%	(18.50%)	2.20%
Net income (loss) (as a percent)	7.30%	6.00%	3.70%	6.50%	(5.30%)	0.20%	(194.70%)	4.00%