Investment Funds Investment Funds (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Unfunded commitments	$ 442,000
Investment funds	1,119,907		$ 1,198,146
Income (Loss) from Investment Funds	50,744	$ 60,385
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds	614,508		641,783
Income (Loss) from Investment Funds	30,661	33,028
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds	85,817		91,448
Income (Loss) from Investment Funds	(12,763)	7,174
Hedge equity
Schedule of Equity Method Investments [Line Items]
Investment funds	0		73,913
Income (Loss) from Investment Funds	(1,164)	791
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds	419,582		$ 391,002
Income (Loss) from Investment Funds	$ 34,010	$ 19,392