Investment Funds (Schedule of Investment Funds) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Investment funds	$ 1,198,146	$ 1,170,040
Income (Losses)	99,301	62,228	$ 131,649
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds	641,783	580,830
Income (Losses)	50,415	58,032	26,233
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds	91,448	93,719
Income (Losses)	19,747	(37,373)	12,797
Hedged equity
Schedule of Equity Method Investments [Line Items]
Investment funds	73,913	70,580
Income (Losses)	3,334	(2,762)	10,760
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds	391,002	424,911
Income (Losses)	$ 25,805	$ 44,331	$ 81,859