Organization and Basis of Presentation (Detail) $ in Millions	3 Months Ended	6 Months Ended
	May. 31, 2015	May. 31, 2015 segment	May. 31, 2014 USD ($)
Organization And Basis Of Presentation [Line Items]
Percent of accounts transfered	50.00%
Number of operating segments | segment		2
Increase (decrease) in receivables from brokers, dealers and clearing organization			$ (30.3)
Increase (decrease) in receivable from customers			30.3
Increase (decrease) in payables to brokers, dealers and clearing organization			13.3
Increase (decrease) in payables to customers			$ (13.3)
3.875% Convertible Senior Debentures due 2029 [Member]
Organization And Basis Of Presentation [Line Items]
Convertible Senior Debentures, interest rate	3.875%	3.875%