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Long-Term Debt (Narrative) (Details) (USD $)
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3 Months Ended |
0 Months Ended |
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Mar. 31, 2015
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Mar. 31, 2014
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Dec. 07, 2012
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Dec. 31, 2014
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Mar. 30, 2014
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| Debt Instrument [Line Items] |
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| Gain on debt extinguishment |
$ 264,000us-gaap_GainsLossesOnExtinguishmentOfDebt
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$ 0us-gaap_GainsLossesOnExtinguishmentOfDebt
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| Long-Term Debt |
306,829,000us-gaap_LongTermDebt
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312,426,000us-gaap_LongTermDebt
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| Revolving Credit Facility [Member] |
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| Debt Instrument [Line Items] |
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| Line of Credit Facility, Maximum Borrowing Capacity |
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300,000,000.0us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
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200,000,000.00us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
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| Line of Credit Facility, Borrowing Capacity Increase Limit |
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100,000,000.0era_LineofCreditFacilityBorrowingCapacityIncreaseLimit
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
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| Remaining borrowing capacity |
209,200,000us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
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| Letters of credit outstanding |
800,000us-gaap_LettersOfCreditOutstandingAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
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| Debt Issuance Cost |
2,400,000us-gaap_DebtIssuanceCosts
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
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| Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |
0.50%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
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| Letter of Credit [Member] |
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| Debt Instrument [Line Items] |
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| Line of Credit Facility, Maximum Borrowing Capacity |
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50,000,000.0us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_LetterOfCreditMember
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| Revolving Credit Facility [Member] |
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| Debt Instrument [Line Items] |
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| Long-Term Debt |
90,000,000us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_RevolvingCreditFacilityMember
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85,000,000us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_RevolvingCreditFacilityMember
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| Secured Debt [Member] |
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| Debt Instrument [Line Items] |
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| Long-Term Debt |
26,729,000us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
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27,426,000us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
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| Payments on other long-term debt |
700,000us-gaap_RepaymentsOfLongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
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| Base Rate [Member] | Revolving Credit Facility [Member] |
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| Debt Instrument [Line Items] |
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| Debt Instrument, Basis Spread on Variable Rate |
1.25%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_VariableRateAxis
= us-gaap_BaseRateMember
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| London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] |
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| Debt Instrument [Line Items] |
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| Debt Instrument, Basis Spread on Variable Rate |
2.25%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember
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| Maximum [Member] | Revolving Credit Facility [Member] |
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| Debt Instrument [Line Items] |
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| Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |
0.50%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
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| Maximum [Member] | Base Rate [Member] | Revolving Credit Facility [Member] |
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| Debt Instrument [Line Items] |
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| Debt Instrument, Basis Spread on Variable Rate |
2.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_BaseRateMember
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| Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] |
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| Debt Instrument [Line Items] |
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| Debt Instrument, Basis Spread on Variable Rate |
3.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember
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| Minimum [Member] | Revolving Credit Facility [Member] |
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| Debt Instrument [Line Items] |
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| Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |
0.375%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
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| Minimum [Member] | Base Rate [Member] | Revolving Credit Facility [Member] |
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| Debt Instrument [Line Items] |
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| Debt Instrument, Basis Spread on Variable Rate |
0.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_BaseRateMember
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| Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] |
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| Debt Instrument [Line Items] |
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| Debt Instrument, Basis Spread on Variable Rate |
1.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember
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| Senior Unsecured Notes Due December 15, 2022 [Member] | 7.750%Senior Notes [Member] |
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| Debt Instrument [Line Items] |
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| Face amount |
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200,000,000.0us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= era_SeniorUnsecuredNotesDueDecember152022Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
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| Stated interest rate |
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7.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= era_SeniorUnsecuredNotesDueDecember152022Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
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| Gain on debt extinguishment |
300,000us-gaap_GainsLossesOnExtinguishmentOfDebt
/ us-gaap_DebtInstrumentAxis
= era_SeniorUnsecuredNotesDueDecember152022Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
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| Repurchase amount |
9,900,000us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_DebtInstrumentAxis
= era_SeniorUnsecuredNotesDueDecember152022Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
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| Proceeds from issuance of long-term debt |
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$ 191,900,000us-gaap_ProceedsFromIssuanceOfLongTermDebt
/ us-gaap_DebtInstrumentAxis
= era_SeniorUnsecuredNotesDueDecember152022Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
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