Annual report pursuant to Section 13 and 15(d)

LONG-TERM DEBT - Company Borrowings (Details)

v2.4.1.9
LONG-TERM DEBT - Company Borrowings (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 07, 2012
Debt Instrument [Line Items]      
Long-term Debt $ 312,426us-gaap_LongTermDebt $ 285,311us-gaap_LongTermDebt  
Portion due with one year (27,426)us-gaap_LongTermDebtCurrent (2,787)us-gaap_LongTermDebtCurrent  
Unamortized discount (2,882)us-gaap_DebtInstrumentUnamortizedDiscount (3,133)us-gaap_DebtInstrumentUnamortizedDiscount  
Long-term debt 282,118us-gaap_LongTermDebtNoncurrent 279,391us-gaap_LongTermDebtNoncurrent  
Secured Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt 27,426us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
30,311us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
 
7.750% Senior Notes [Member] | Senior Notes [Member]      
Debt Instrument [Line Items]      
Long-term Debt 200,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= era_Senior7Point750PercentNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
200,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= era_Senior7Point750PercentNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
200,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= era_Senior7Point750PercentNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Revolving Credit Facility [Member] | Secured Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt $ 85,000us-gaap_LongTermDebt
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
$ 55,000us-gaap_LongTermDebt
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember