Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at	$ 37,692	$ (16,507)
Unrealized gains (losses)	(24,566)	54,585
Amounts reclassified from accumulated other comprehensive income (loss)	(9,885)	(386)
Balance at	3,241	37,692
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at	565	2,244
Unrealized gains (losses)	3,677	168
Amounts reclassified from accumulated other comprehensive income (loss)	(1,692)	(1,847)
Balance at	2,550	565
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at	31,112	(18,286)
Unrealized gains (losses)	(22,516)	48,482
Amounts reclassified from accumulated other comprehensive income (loss)	(5,736)	916
Balance at	2,860	31,112
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at	6,015	(465)
Unrealized gains (losses)	(5,727)	5,935
Amounts reclassified from accumulated other comprehensive income (loss)	(2,457)	545
Balance at	$ (2,169)	$ 6,015