Investments (Other Long Term Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Other Long Term Investments [Line Items]
Total other long-term investments	$ 182,157	$ 162,783
Joint ventures and limited partnerships
Other Long Term Investments [Line Items]
Total other long-term investments	66,890	68,225
Derivatives
Other Long Term Investments [Line Items]
Total other long-term investments	$ 115,267	$ 94,558