Variable Interest Entities - Non-consolidated VIEs - Additional Information (Detail) - USD ($)	Nov. 30, 2016	Nov. 30, 2015
Variable Interest Entity [Line Items]
Maximum exposure	$ 313,100,000
Agency mortgage-backed securities [Member]
Variable Interest Entity [Line Items]
Carrying amount	1,002,200,000	$ 3,359,100,000
Non agency mortgage-backed securities [Member]
Variable Interest Entity [Line Items]
Carrying amount	439,400,000	630,500,000
Private equity vehicles [Member] | JCP Entities [Member]
Variable Interest Entity [Line Items]
Equity commitments amount	148,100,000
Funded equity commitments	125,100,000	124,600,000
Carrying amount of equity investment	37,600,000	39,300,000
Private equity vehicles [Member] | Jefferies Energy Partners I LP [Member]
Variable Interest Entity [Line Items]
Maximum exposure	3,000,000.0	3,000,000.0
Other Private Investment Vehicles [Member]
Variable Interest Entity [Line Items]
Equity commitments amount	75,800,000	50,800,000
Funded equity commitments	74,300,000	49,300,000
Carrying amount of equity investment	$ 52,300,000	$ 51,300,000