Investments (Other Long Term Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Other Long Term Investments
Other long-term investments	$ 344,463	$ 379,237
Company’s investment in separate accounts
Other Long Term Investments
Other long-term investments	34,088	28,567
Private Equity Funds
Other Long Term Investments
Other long-term investments	139,493	140,310
Hedge Funds
Other Long Term Investments
Other long-term investments	81,104	130,575
Real Estate Properties
Other Long Term Investments
Other long-term investments	11,912	9,685
Joint ventures and limited partnerships
Other Long Term Investments
Other long-term investments	232,509	280,570
Derivatives
Other Long Term Investments
Other long-term investments	$ 77,866	$ 70,100