Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	$ (16,507)
Unrealized gains	7,788
Amounts reclassified from accumulated other comprehensive income	113
Balance at September 30, 2013	(8,606)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	2,244
Unrealized gains	1,197
Amounts reclassified from accumulated other comprehensive income	(1,339)
Balance at September 30, 2013	2,102
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(18,286)
Unrealized gains	1,938
Amounts reclassified from accumulated other comprehensive income	1,252
Balance at September 30, 2013	(15,096)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(465)
Unrealized gains	4,653
Amounts reclassified from accumulated other comprehensive income	200
Balance at September 30, 2013	$ 4,388