Variable Interest Entities - Non-consolidated VIEs - Additional Information (Detail) - USD ($)	Feb. 28, 2017	Nov. 30, 2016
Variable Interest Entity [Line Items]
Maximum exposure	$ 134,100,000
Agency mortgage-backed securities [Member]
Variable Interest Entity [Line Items]
Carrying amount	1,761,900,000	$ 1,002,200,000
Non agency mortgage-backed securities [Member]
Variable Interest Entity [Line Items]
Carrying amount	351,900,000	439,400,000
Related party private equity vehicles [Member] | JCP Entities [Member]
Variable Interest Entity [Line Items]
Equity investments	148,100,000
Funded equity commitments	125,400,000	125,100,000
Carrying amount of equity investment	36,300,000	37,600,000
Related party private equity vehicles [Member] | Jefferies Energy Partners I LP [Member]
Variable Interest Entity [Line Items]
Maximum exposure	3,000,000	3,000,000.0
Other private investment vehicles [Member]
Variable Interest Entity [Line Items]
Equity investments	65,000,000	75,800,000
Funded equity commitments	63,500,000	74,300,000
Carrying amount of equity investment	$ 51,600,000	$ 52,300,000