Long-term Debt Terminated Debt Agreements (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 18, 2011	Sep. 28, 2012
Debt Instrument [Line Items]
Loss on extinguishment of debt	$ (146,800,000)	$ (4,132,000)	$ (146,787,000)	$ (51,796,000)
Opco [Member]
Debt Instrument [Line Items]
Loss on extinguishment of debt				51,800,000
Opco [Member] | Term Loan Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					435,700,000
Opco [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					25,000,000
GVR Lenders [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					10,000,000
GVR Lenders [Member] | First Lien Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					215,000,000
GVR Lenders [Member] | Second Lien Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					90,000,000
Opco and GVR [Member] | Term Loan Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount						575,000,000
Opco and GVR [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity						$ 200,000,000