Variable Interest Entities - Non-consolidated VIEs - Additional Information (Detail) - USD ($) $ in Millions	May 31, 2017	Nov. 30, 2016
Variable Interest Entity [Line Items]
Maximum exposure	$ 149.4
Agency mortgage-backed securities [Member]
Variable Interest Entity [Line Items]
Carrying amount	1,713.3	$ 1,002.2
Non agency mortgage-backed securities [Member]
Variable Interest Entity [Line Items]
Carrying amount	248.8	439.4
Related party private equity vehicles [Member] | JCP Entities [Member]
Variable Interest Entity [Line Items]
Equity investments	148.1
Funded equity commitments	125.4	125.1
Carrying amount of equity investment	28.0	37.6
Related party private equity vehicles [Member] | Jefferies Energy Partners I LP [Member]
Variable Interest Entity [Line Items]
Maximum exposure		3.0
Other private investment vehicles [Member]
Variable Interest Entity [Line Items]
Equity investments	62.5	75.8
Funded equity commitments	61.0	74.3
Carrying amount of equity investment	$ 51.6	$ 52.3