Investments (Gains (Losses) Related to Trading Securities) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Net (losses) gains recognized during the period	$ (1,432)	$ 10,957	$ 5,352	$ 25,769
Less: net gains recognized during the period on trading securities sold during the period	506	3,462	6,553	7,866
Unrealized (losses) gains recognized during the period on trading securities held	$ (1,938)	$ 7,495	$ (1,201)	$ 17,903