Variable Interest Entities - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Nonconsolidated VIEs, assets carrying amount	$ 1,107,900	$ 746,400
Investment in associated company	1,652,957	2,417,332	$ 2,066,829	$ 2,125,098
Related party private equity vehicles
Variable Interest Entity [Line Items]
Nonconsolidated VIEs, assets carrying amount	23,000	35,500
Other investment vehicles
Variable Interest Entity [Line Items]
Carrying amount of equity investment	574,000	203,600
Unfunded equity commitment related to investments	192,100	11,100
Nonconsolidated VIEs, assets carrying amount	574,000	203,600
Agency mortgage-backed securities
Variable Interest Entity [Line Items]
Nonconsolidated VIEs, assets carrying amount	1,453,500	2,913,000
Non-agency mortgage- and other asset-backed securities
Variable Interest Entity [Line Items]
Nonconsolidated VIEs, assets carrying amount	134,800	170,500
Securitization Vehicles
Variable Interest Entity [Line Items]
Automobile loan receivables securitized	227,400
JCP Entities | Related party private equity vehicles
Variable Interest Entity [Line Items]
Equity commitments	133,000	139,300
Funded equity commitments	121,700	121,300
Carrying amount of equity investment	23,000	$ 35,500
Investment in FXCM
Variable Interest Entity [Line Items]
Fair value of senior secured term loan receivable	59,100
Investment in associated company	70,200
Senior secured term loan receivable and investments in associated companies	$ 129,300