Investment Funds Investment Funds (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Unfunded commitments	$ 354,000
Investment funds	1,190,963		$ 1,198,146
Income (Loss) from Investment Funds	35,544	$ 35,092
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds	611,598		641,783
Income (Loss) from Investment Funds	19,518	22,414
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds	86,690		91,448
Income (Loss) from Investment Funds	(8,639)	1,153
Hedge equity
Schedule of Equity Method Investments [Line Items]
Investment funds	72,685		73,913
Income (Loss) from Investment Funds	(1,228)	(2,030)
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds	419,990		$ 391,002
Income (Loss) from Investment Funds	$ 25,893	$ 13,555