Income Taxes Net Deferred Tax assets/Liabilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Postretirement Benefits	$ 337,836,000	$ 347,584,000
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Asset Retirement Obligations	37,306,000	57,370,000
Deferred Tax Assets, Property, Plant and Equipment	22,489,000	23,103,000
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	159,933,000	54,609,000
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits	44,580,000	46,164,000
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Other	31,008,000	25,191,000
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Pensions	14,330,000	83,077,000
Deferred Tax Assets, Operating Loss Carryforwards	168,658,000	27,277,000
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities	35,655,000	20,804,000
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals	20,978,000	26,716,000
Deferred Tax Assets, Other	160,567,000	149,435,000
Deferred Tax Assets, Gross	1,033,340,000	861,330,000
Deferred Tax Assets, Valuation Allowance	7,532,000	4,500,000
Deferred Tax Assets	1,025,808,000	856,830,000
Deferred Tax Liabilities, Property, Plant and Equipment	(954,007,000)	(976,505,000)
Deferred Tax Liabilities, Derivatives	(27,741,000)	(51,006,000)
Deferred Tax Liabilities, Leasing Arrangements	(38,105,000)	(33,950,000)
Deferred Tax Liabilities, Other	(37,295,000)	(37,277,000)
Deferred Tax Liabilities, Gross	(1,057,148,000)	(1,098,738,000)
Deferred Tax Liabilities, Net	(31,340,000)	(241,908,000)
Deferred Federal Income Tax Expense (Benefit)	51,765	27,277
Valuation Allowance, Deferred Tax Asset, Change in Amount	$ 4,000