Rollforward of Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2012	$ (8,311)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	568
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(12,324)
Other Comprehensive Income (Loss), Net of Tax	(11,756)
Balance as of December 31, 2013	(20,067)
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2012	44,196
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(11,014)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(21,004)
Other Comprehensive Income (Loss), Net of Tax	(32,018)
Balance as of December 31, 2013	12,178
Pension and Postretirement Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2012	(52,507)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	11,582
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	8,680
Other Comprehensive Income (Loss), Net of Tax	20,262
Balance as of December 31, 2013	$ (32,245)