Variable Interest Entities - Non-consolidated VIEs - Additional Information (Detail)	6 Months Ended
	May 31, 2016 USD ($) aircraft	Nov. 30, 2015 USD ($)
Variable Interest Entity [Line Items]
Maximum exposure	$ 363,500,000
Agency mortgage-backed securities [Member]
Variable Interest Entity [Line Items]
Carrying amount	1,647,700,000	$ 3,359,100,000
Non agency mortgage-backed securities [Member]
Variable Interest Entity [Line Items]
Carrying amount	527,000,000	630,500,000
Related party private equity vehicles [Member] | JCP Entities [Member]
Variable Interest Entity [Line Items]
Equity investments	148,100,000
Funded equity commitments	124,900,000	124,600,000
Carrying amount of equity investment	32,000,000	39,300,000
Related party 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 investments	75,800,000	50,800,000
Funded equity commitments	74,300,000	49,300,000
Carrying amount of equity investment	$ 58,000,000	$ 51,300,000
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Number of Aircrafts For Purchase and Lease | aircraft	5