Investment Funds (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Unfunded commitments		$ 241,000
Investment funds		1,401,571	$ 1,332,818
Income (Loss) from Investment Funds	$ 53,070	58,251
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds		654,610	642,137
Income (Loss) from Investment Funds	35,826	13,078
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds		75,053	75,213
Income (Loss) from Investment Funds	(1,256)	(7,100)
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds		671,908	$ 615,468
Income (Loss) from Investment Funds	$ 18,500	$ 52,273