Investment Funds (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Unfunded commitments	$ 263,000
Investment funds	1,227,298		$ 1,332,818
Income (Loss) from Investment Funds	77,284	$ 94,075
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds	437,000		642,137
Income (Loss) from Investment Funds	17,279	50,044
Financial services
Schedule of Equity Method Investments [Line Items]
Investment funds	282,630		195,706
Income (Loss) from Investment Funds	36,516	8,201
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds	173,508		183,627
Income (Loss) from Investment Funds	(10,342)	14,088
Transportation
Schedule of Equity Method Investments [Line Items]
Investment funds	146,264		136,640
Income (Loss) from Investment Funds	12,222	11,270
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds	187,896		$ 174,708
Income (Loss) from Investment Funds	$ 21,609	$ 10,472