Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at	$ 3,241	$ 37,692
Unrealized gains (losses)	(8,153)	(24,566)
Amounts reclassified from accumulated other comprehensive income (loss)	3,097	(9,885)
Balance at	(1,815)	3,241
Derivative Instruments [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at	2,550	565
Unrealized gains (losses)	3,903	3,677
Amounts reclassified from accumulated other comprehensive income (loss)	(6,128)	(1,692)
Balance at	325	2,550
Pension, Postretirement and Other Post-Employment Benefits [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at	2,860	31,112
Unrealized gains (losses)	(8,723)	(22,516)
Amounts reclassified from accumulated other comprehensive income (loss)	5,142	(5,736)
Balance at	(721)	2,860
Available-for-Sale Securities [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at	(2,169)	6,015
Unrealized gains (losses)	(3,333)	(5,727)
Amounts reclassified from accumulated other comprehensive income (loss)	4,083	(2,457)
Balance at	$ (1,419)	$ (2,169)