Investment Information - Equity method investments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	$ 1,727,302	$ 1,660,396
Credit related funds
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	624,382	428,437
Equity securities
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	292,499	293,686
Real estate
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	249,822	246,851
Lending
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	137,270	202,690
Private equity
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	181,492	144,983
Infrastructure
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	141,972	235,033
Energy
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	$ 99,865	$ 108,716