Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE, Part 2 (Details)

v2.4.1.9
FAIR VALUE, Part 2 (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]  
Long-term Debt $ 845.7us-gaap_LongTermDebt
Debt Instrument, Unamortized Premium 7.7us-gaap_DebtInstrumentUnamortizedPremium
Asset retirement obligations 0.2us-gaap_AssetRetirementObligation
Carrying Amount [Member]  
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]  
Senior unsecured notes 507.7us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
Revolving credit facility 338.0us-gaap_LinesOfCreditFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
Estimated Fair Value [Member]  
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]  
Senior unsecured notes $ 453.8us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember