Revenues from Contracts with Customers - Components of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2018	May 31, 2017
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 671,219		$ 1,270,728
Revenues	1,156,809	$ 1,038,955	2,243,404	$ 2,048,752
Commissions and other fees
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	158,104		306,006
Investment banking
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	500,297		940,288
Asset management fees
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	6,016		10,946
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	6,802		13,488
Principal transactions
Disaggregation of Revenue [Line Items]
Revenues	137,802		355,275
Interest
Disaggregation of Revenue [Line Items]
Revenues	307,327		565,143
Other
Disaggregation of Revenue [Line Items]
Revenues	$ 40,461		$ 52,258