Basis of Presentation Changes in Accumulated Other Comprehensive Income / (Loss) by component (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (359,715)		$ (359,715)		$ (325,117)
Other Comprehensive Income (Loss), Net of Tax	(9,065)	79,125	(34,598)	83,574
Accumulated Other Comprehensive Income (Loss) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(359,715)		(359,715)		(325,117)
Other comprehensive income before reclassifications			(81,316)
Amounts reclassified from accumulated other comprehensive income			46,718
Other Comprehensive Income (Loss), Net of Tax			(34,598)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	6,574		6,574		42,493
Other comprehensive income before reclassifications			(59,183)
Amounts reclassified from accumulated other comprehensive income			23,264
Other Comprehensive Income (Loss), Net of Tax			(35,919)
Accumulated Defined Benefit Plans Adjustment [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(366,289)		(366,289)		(367,610)
Other comprehensive income before reclassifications			(22,133)
Amounts reclassified from accumulated other comprehensive income			23,454
Other Comprehensive Income (Loss), Net of Tax			$ 1,321