Investment Funds (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Unfunded commitments	$ 225,000
Investment funds	1,178,858		$ 1,213,535
Income (Loss) from Investment Funds	40,577	$ 11,411
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds	328,053		412,275
Income (Loss) from Investment Funds	6,790	10,476
Financial services
Schedule of Equity Method Investments [Line Items]
Investment funds	318,084		280,705
Income (Loss) from Investment Funds	15,209	1,528
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds	152,658		156,869
Income (Loss) from Investment Funds	4,413	(11,793)
Transportation
Schedule of Equity Method Investments [Line Items]
Investment funds	150,353		147,034
Income (Loss) from Investment Funds	2,646	8,602
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds	229,710		$ 216,652
Income (Loss) from Investment Funds	$ 11,519	$ 2,598