Investment Funds (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Unfunded commitments	$ 136,000
Investment funds	1,163,707		$ 1,213,535
Income (Loss) from Investment Funds	1,260	$ 77,284
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds	312,181		412,275
Income (Loss) from Investment Funds	2,140	17,279
Financial services
Schedule of Equity Method Investments [Line Items]
Investment funds	351,695		280,705
Income (Loss) from Investment Funds	3,303	36,516
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds	136,250		156,869
Income (Loss) from Investment Funds	(13,689)	(10,342)
Transportation
Schedule of Equity Method Investments [Line Items]
Investment funds	144,265		147,034
Income (Loss) from Investment Funds	(3,521)	12,222
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds	219,316		$ 216,652
Income (Loss) from Investment Funds	$ 13,027	$ 21,609