Investments (Other Long Term Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Other Long Term Investments [Line Items]
Other long-term investments	$ 551,931	$ 182,157
Private Equity Funds
Other Long Term Investments [Line Items]
Other long-term investments	30,513	22,535
Hedge Funds
Other Long Term Investments [Line Items]
Other long-term investments	98,554	41,820
Real Estate Properties
Other Long Term Investments [Line Items]
Other long-term investments	109,043	2,535
Joint Ventures And Limited Partnerships
Other Long Term Investments [Line Items]
Other long-term investments	238,110	66,890
Derivatives
Other Long Term Investments [Line Items]
Other long-term investments	$ 313,821	$ 115,267