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NATURE OF OPERATIONS AND ACCOUNTING POLICIES - ERA Savings Plan (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract] |  |  |
Percent of employer contribution | 3.00% |  |
Employer matching contribution, percent | 100.00% |  |
Employer matching contribution, percent of employees' gross pay | 3.00% |  |
Employer contribution | $ 2.5 | $ 2.3 | $ 2.4

X
- Definition Defined Contribution Plan, Percent of Employees' Gross Pay + References No definition available. + Details
Name: | era_DefinedContributionPlanPercentofEmployeesGrossPay
Namespace Prefix: | era_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration