Investments - Jefferies Finance - Narrative (Detail) - USD ($)	6 Months Ended
	May 31, 2017	Nov. 30, 2016
Guarantee Obligations [Line Items]
Funded portion of loan commitment		$ 0
Loan commitment		250,000,000
Financial instruments, owned, at fair value	$ 13,881,283,000	13,809,512,000
Financial instruments sold, not yet purchased, at fair value	9,004,535,000	8,359,202,000
Jefferies Finance, LLC [Member]
Guarantee Obligations [Line Items]
Equity commitment	600,000,000
Total committed equity capitalization of JIFN	1,200,000,000
Funded portion of equity commitment to subsidiary	516,900,000
Unfunded portion of equity commitment to subsidiary	$ 83,100,000
Extension period	1 year
Termination notice period	60 days
Funded portion of loan commitment	$ 0
Loan commitment	250,000,000
Financial instruments, owned, at fair value	100,000
Financial instruments sold, not yet purchased, at fair value		4,000
Jefferies Finance, LLC [Member] | Corporate debt securities [Member]
Guarantee Obligations [Line Items]
Committed line of credit facility amount	500,000,000
Other Assets [Member] | Jefferies Finance, LLC [Member]
Guarantee Obligations [Line Items]
Receivables under service agreement	$ 16,500,000
Accounts Payable and Accrued Liabilities [Member] | Jefferies Finance, LLC [Member]
Guarantee Obligations [Line Items]
Payables under service agreement		$ 5,800,000