Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest [Abstract]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (24,935)	$ (12,813)	$ 91,069	$ (14,634)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax, Portion Attributable to Parent [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(3,798)	42,904	1,321	88,661
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	(12,218)	45,749	(59,183)	27,154
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred	6,951	(9,528)	23,264	(32,241)
Other Comprehensive Income (Loss), Net of Tax	(9,065)	79,125	(34,598)	83,574
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	(34,000)	66,312	56,471	68,940
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	0	(287)	0	(544)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ (34,000)	$ 66,599	$ 56,471	$ 69,484