Note 14 - Subsequent Events (Details Textual) - Subsequent Event [Member] - IsoBoost Supply Commitment [Member] $ in Millions	Jul. 18, 2016 USD ($)
Long-term Contract, Potential Amount	$ 11
Long-term Contract, Initial Amount	7
Long-term Contract, Potential Additional Amount	$ 4

Potential additional amount to be received from customers under long-term contracts or programs for which revenue has yet to be earned.

No definition available.

Name:	erii_LongtermContractPotentialAdditionalAmount
Namespace Prefix:	erii_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant