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Long-Term Debt Debt Maturity Schedule (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2014
Debt Instrument [Line Items]
Long-term Debt	$ 3,241,474us-gaap_LongTermDebt	$ 3,118,920us-gaap_LongTermDebt
Senior Notes		0us-gaap_SeniorNotes
Less amounts due in one year	(5,052)us-gaap_LongTermDebtCurrent	(2,957)us-gaap_LongTermDebtCurrent
Long-Term Debt	3,236,422us-gaap_LongTermDebtNoncurrent	3,115,963us-gaap_LongTermDebtNoncurrent
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	4,480
Long-term Debt, Maturities, Repayments of Principal in Year Two	4,454
Long-term Debt, Maturities, Repayments of Principal in Year Three	2,944
Long-term Debt, Maturities, Repayments of Principal in Year Four	1,266
Long-term Debt, Maturities, Repayments of Principal in Year Five	904
Long-term Debt, Maturities, Repayments of Principal after Year Five	3,235,692
Long-term Debt	3,249,740us-gaap_DebtInstrumentCarryingAmount
Senior Notes Due April 2017 at 8.00%
Debt Instrument [Line Items]
Long-term Debt	0	1,500,000
Senior notes due April 2020 at 8.25%
Debt Instrument [Line Items]
Long-term Debt	1,014,800	1,250,000
Senior notes due March 2021 at 6.375%
Debt Instrument [Line Items]
Long-term Debt	250,000	250,000
Senior Secured Notes Due April 2022 Par Value [Member]
Debt Instrument [Line Items]
Long-term Debt			1,856,506
Baltimore Port Facility revenue bonds in series due September 2025 at 5.75%
Debt Instrument [Line Items]
Long-term Debt	102,865	102,865
Advance royalty commitments
Debt Instrument [Line Items]
Long-term Debt	13,473	11,182
Note due through December 2012 at 6.10%
Debt Instrument [Line Items]
Long-term Debt	$ 3,830	$ 4,873