Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Remaining Unfunded Commitments to Venture Capital or Private Equity Funds by our Consolidated Managed Funds (Details) $ in Thousands	Sep. 30, 2020 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Unfunded Commitments	$ 4,406
Strategic Investors Fund, LP
Commitments and Contingencies Disclosure [Line Items]
Unfunded Commitments	376
Capital Preferred Return Fund, LP
Commitments and Contingencies Disclosure [Line Items]
Unfunded Commitments	1,517
Growth Partners, LP
Commitments and Contingencies Disclosure [Line Items]
Unfunded Commitments	$ 2,513