Investment Information - Equity method investments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	$ 2,256,327	$ 2,047,889
Credit related funds
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	818,344	740,060
Equity securities
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	357,641	343,058
Real estate
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	292,424	258,518
Lending
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	199,913	179,629
Private equity
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	288,657	235,289
Infrastructure
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	179,225	175,882
Energy
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	$ 120,123	$ 115,453