Basis of Presentation Reclassification of adjustments out of Accumulated Other Comprehensive Loss (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
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Natural Gas Swaps	$ 13,593	$ (18,088)	$ 40,857	$ (54,767)
Tax Benefit of Natural Gas Swaps	(6,642)	8,560	(17,593)	22,526
Natural Gas Swaps, Net of Tax	6,951	(9,528)	23,264	(32,241)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(2,542)	(8,211)	(5,084)	(16,423)
Defined Benefit Plan, Amortization of Gains (Losses)	10,861	23,559	21,507	48,747
Other Comprehensive Income (Loss), Finalization of Pension and Non-Pension Postretirement Plan Valuation, Net of Tax	20,707	5,087	20,707	32,202
Net periodic (benefit) cost	29,026	20,435	37,130	64,526
Tax Expense on Actuarially Determined Long-Term Liabilities	(10,691)	(7,800)	(13,676)	(24,631)
Actuarially Determined Long-Term Liability Adjustments, Net of Tax	18,335	12,635	23,454	39,895
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(346)	(407)	(692)	(815)
Defined Benefit Plan, Amortization of Gains (Losses)	6,106	10,547	11,997	22,722
Other Comprehensive Income (Loss), Finalization of Pension and Non-Pension Postretirement Plan Valuation, Net of Tax	20,707	5,087	20,707	32,202
Net periodic (benefit) cost	$ 27,178	$ 17,006	$ 33,435	$ 58,293