Related Party Transactions - Jefferies (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2020	Aug. 31, 2019	Nov. 30, 2019
Related Party Transaction [Line Items]
Payables-brokers, dealers and clearing organizations		$ 2,546,494,000		$ 2,546,494,000		$ 2,555,178,000
Financial instruments owned, at fair value		17,555,720,000		17,555,720,000		16,363,374,000
Financial instruments sold, not yet purchased		10,994,445,000		10,994,445,000		10,532,460,000
Corporate debt securities
Related Party Transaction [Line Items]
Financial instruments sold, not yet purchased		1,448,706,000		1,448,706,000		1,471,482,000
Affiliated Entity | Director
Related Party Transaction [Line Items]
Investment in related party						3,600,000
Jefferies | Affiliated Entity
Related Party Transaction [Line Items]
Charges to Jefferies for services provided		13,800,000	$ 9,800,000	34,300,000	$ 36,100,000
Charges from Jefferies for services received		4,200,000	6,400,000	19,600,000	7,800,000
Receivable from Jefferies		3,200,000		3,200,000		900,000
Payable to Jefferies		0		0		4,300,000
Payments of distributions to affiliates				164,700,000
Distribution payable		134,000,000.0		134,000,000.0
Net current tax payable		206,700,000		206,700,000
Net current tax receivable						24,400,000
Payments of payable to Jefferies		10,000,000.0		42,000,000.0
Net gain (loss) on investments				0
Securities purchased from Jefferies		20,200,000	0	60,100,000	885,600,000
Securities sold to Jefferies		100,000	22,900,000	100,000	40,800,000
Payables-brokers, dealers and clearing organizations		2,700,000		2,700,000		9,900,000
Receipt of payment from Jefferies for transfer of one of its asset management divisions	$ 2,900,000
Jefferies | Affiliated Entity | Corporate debt securities
Related Party Transaction [Line Items]
Financial instruments owned, at fair value		2,500,000		2,500,000		100,000
Jefferies | Affiliated Entity | Investment banking
Related Party Transaction [Line Items]
Charges to Jefferies for services provided		0	2,400,000	0	10,300,000
Jefferies | Affiliated Entity | Commissions and other fees
Related Party Transaction [Line Items]
Charges to Jefferies for services provided		400,000	1,100,000	1,100,000	2,300,000
Affiliate of Jefferies Financial Group Inc. | Affiliated Entity
Related Party Transaction [Line Items]
Financial instruments owned, at fair value		100,000		100,000		0
Payments for rent and other expenses		200,000		600,000
Subsidiary of Jefferies Financial Group Inc. | Affiliated Entity
Related Party Transaction [Line Items]
Financial instruments sold, not yet purchased		600,000		600,000		600,000
Net gains on foreign exchange contracts		600,000	1,200,000	1,600,000	1,900,000
Hedge Fund Managed by Jefferies | Affiliated Entity
Related Party Transaction [Line Items]
Net gain (loss) on investments		7,700,000	$ 1,000,000.0	14,000,000.0	$ 3,300,000
Investment in related party		$ 237,000,000.0		$ 237,000,000.0		223,500,000
Hedge Fund Managed by Jefferies | Affiliated Entity | Director
Related Party Transaction [Line Items]
Investment in related party						$ 400,000