Cash collateral balance as a percentage of outstanding debt required by a credit agreement.

No definition available.

Name:	erii_CashCollateralBalanceRequiredByCreditAgreement
Namespace Prefix:	erii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The fee, expressed as a percentage of face amount of the letter of credit, that are payable quarterly and are non-refundable.

+ References

No definition available.

+ Details

Name:	erii_StandbyLettersOfCreditFeePercentage
Namespace Prefix:	erii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=erii_LoanAndPledgeAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=erii_UncommittedRevolvingCreditLineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=erii_CommittedRevolvingCreditLineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Long-term Debt and Lines of Credit - Loan Agreements and Stand-by Letters of Credit (Details) - USD ($)		1 Months Ended
	Jan. 27, 2017	Jun. 30, 2015	Aug. 24, 2018	Jan. 24, 2017
The 2012 Agreement \| Financial Institution 1
Line of Credit Facility [Line Items]
Cash collateral balance required by credit agreement		101.00%		105.00%
The 2012 Agreement \| Revolving Credit Facility \| Financial Institution 1
Line of Credit Facility [Line Items]
Unused capacity, commitment fee percentage		0.25%
Loan and Pledge Agreement \| Financial Institution 2
Line of Credit Facility [Line Items]
Standby letters of credit, fee percentage	0.70%
Loan and Pledge Agreement \| Uncommitted Revolving Credit Line \| Financial Institution 2
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 4,000,000.0
Loan and Pledge Agreement \| Committed Revolving Credit Line \| Financial Institution 2
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 16,000,000.0
Foreign Subsidiary \| Loan and Pledge Agreement \| Financial Institution 2
Line of Credit Facility [Line Items]
Maximum borrowing capacity			$ 66,000,000.0