Annual report pursuant to Section 13 and 15(d)

GUARANTORS OF SECURITIES GUARANTORS OF SECURITIES (Details)

v2.4.1.9
GUARANTORS OF SECURITIES GUARANTORS OF SECURITIES (Details) (Senior Notes [Member], USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 07, 2012
Debt Instrument [Line Items]      
Stated interest rate     7.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
7.750% Senior Notes [Member]      
Debt Instrument [Line Items]      
Face amount     $ 200.0us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= era_Senior7Point750PercentNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Stated interest rate 7.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= era_Senior7Point750PercentNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		7.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= era_Senior7Point750PercentNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember 		7.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= era_Senior7Point750PercentNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember