Revenues from Contracts with Customers - Components of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	May 31, 2019	May 31, 2018	May 31, 2019	May 31, 2018
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 602,527	$ 671,219	$ 1,049,921	$ 1,270,728
Revenues	1,314,493	1,156,809	2,369,365	2,243,404
Commissions and other fees
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	159,773	158,104	307,099	306,006
Investment banking
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	430,087	500,297	715,683	940,288
Asset management fees
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	4,550	6,016	11,219	10,946
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,117	6,802	15,920	13,488
Principal transactions
Disaggregation of Revenue [Line Items]
Revenues	248,831	137,802	483,129	355,275
Interest
Disaggregation of Revenue [Line Items]
Revenues	418,451	307,327	779,426	565,143
Other
Disaggregation of Revenue [Line Items]
Revenues	$ 44,684	$ 40,461	$ 56,889	$ 52,258