Investments - Jefferies Finance - Narrative (Detail) - USD ($) $ in Thousands	12 Months Ended
	Nov. 30, 2017	Nov. 30, 2016
Guarantor Obligations [Line Items]
Financial instruments owned, at fair value	$ 13,998,125	$ 13,809,512
Jefferies Finance
Guarantor Obligations [Line Items]
Equity commitment	750,000
Total committed equity capitalization of JIFN	1,500,000
Funded portion of equity commitment to subsidiary	636,200
Unfunded portion of equity commitment to subsidiary	$ 113,800
Extension period	1 year
Termination notice period	60 days
Funded portion of loan commitment	$ 0
Loan commitment	250,000
Financial instruments owned, at fair value	1,500
Jefferies Finance | Committed advances
Guarantor Obligations [Line Items]
Committed line of credit facility amount	500,000
Other Assets | Jefferies Finance
Guarantor Obligations [Line Items]
Receivables under service agreement	$ 20,500
Accounts expenses and other liabilities | Jefferies Finance
Guarantor Obligations [Line Items]
Payables under service agreement		$ 5,800