Components of Working Capital - Accrued Liabilities Table (details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Accrued Liabilities [Line Items]
Other accrued liabilities	$ 293		$ 1,561
Accrued interest expense	16,620		15,868
Short-term asset retirement obligations	1,187		1,711
Short-term remediation and reclamation obligations	609		799
Accrued liabilities	140,323	[1]	148,600	[1],[2]
Accrued Capital Expenditures [Member]
Accrued Liabilities [Line Items]
Other accrued liabilities	100,876		112,311
Accrued Plant Purchases [Member]
Accrued Liabilities [Line Items]
Other accrued liabilities	$ 20,738		$ 16,350

[1] Accrued liabilities include amounts payable to affiliates of $0.1 million as of September 30, 2013 and December 31, 2012.

[2] Financial information has been recast to include the financial position and results attributable to the Non-Operated Marcellus Interest. See Note 2.