Variable Interest Entities - Non-consolidated VIEs - Additional Information (Detail) - USD ($) $ in Millions	Aug. 31, 2017	Nov. 30, 2016
Variable Interest Entity [Line Items]
Maximum exposure	$ 245.5
Agency mortgage-backed securities
Variable Interest Entity [Line Items]
Carrying amount	2,026.7	$ 1,002.2
Non agency mortgage-backed securities
Variable Interest Entity [Line Items]
Carrying amount	272.4	439.4
Related party private equity vehicles | JCP Entities
Variable Interest Entity [Line Items]
Equity investments	148.1
Funded equity commitments	126.3	125.1
Carrying amount of equity investment	28.1	37.6
Related party private equity vehicles | Jefferies Energy Partners I, LP
Variable Interest Entity [Line Items]
Maximum exposure		3.0
Other private investment vehicles
Variable Interest Entity [Line Items]
Equity investments	62.5	75.8
Funded equity commitments	61.0	74.3
Carrying amount of equity investment	$ 52.0	$ 52.3