Commitments and Contingencies - Schedule of limited partners' callable commitments (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	$ 442.8	$ 486.8
Real Estate Funds
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	304.6	321.1
Real Estate Funds | Veritas Trophy VI, LLC
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	20.0	20.6
Real Estate Funds | SP V - II, LLC
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	12.9	12.9
Real Estate Funds | JCR Capital - REA Preferred Equity Parallel Fund
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	76.1	75.3
Real Estate Funds | Silverpeak NRE FundCo 2 LLC
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	41.8	43.7
Real Estate Funds | Silverpeak NRE FundCo LLC
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	30.0	37.3
Real Estate Funds | Taconic New York City GP Fund
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	4.2	4.2
Real Estate Funds | Flagler - REA Healthcare Properties Partnership
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	1.2	1.2
Real Estate Funds | Townsend Group Value-Add Fund
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	118.4	125.9
Loans Receivable
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	138.2	165.7
Loans Receivable | BREP VIII Industrial Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	0.0	22.4
Loans Receivable | 311 South Wacker Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	2.2	2.2
Loans Receivable | San Diego Office Portfolio Senior Loan
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	5.9	6.8
Loans Receivable | San Diego Office Portfolio Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	2.0	2.2
Loans Receivable | MRA Hub 34 Holding, LLC
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	1.5	1.5
Loans Receivable | 1330 Broadway Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	10.9	10.9
Loans Receivable | Liberty Park Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	2.6	2.6
Loans Receivable | Colony New England Hotel Portfolio Senior Loan
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	14.1	14.1
Loans Receivable | Colony New England Hotel Portfolio Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	4.7	4.7
Loans Receivable | Exo Apartments Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	2.4	2.4
Loans Receivable | SCG Oakland Portfolio Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	5.8	6.1
Loans Receivable | Five Oak Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	1.6	1.6
Loans Receivable | 5 Points Towers Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	4.0	4.2
Loans Receivable | The Stratum Senior Loan
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	2.0	2.0
Loans Receivable | The Stratum Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	0.7	0.7
Loans Receivable | Spring House Innovation Park Senior Loan
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	35.4	38.0
Loans Receivable | Spring House Innovation Park Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	11.8	12.7
Loans Receivable | The Reserve at Chino Hills
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	20.0	20.0
Loans Receivable | Sixth and Main Senior Loan
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	6.9	6.9
Loans Receivable | Sixth and Main Mezzanine
Limited Partners' Capital Account [Line Items]
TOTAL COMMITMENTS	$ 3.7	$ 3.7