Other Financial Information - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Other Financial Information [Abstract]
Payroll and commissions payable	$ 4,782	$ 6,071
Other accrued expenses and current liabilities	1,864	1,877
Total accrued expenses and other current liabilities	$ 6,646	$ 7,948

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, are related to services received from employees, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities, accrued salaries and bonuses, payroll taxes and fringe benefits. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). This element is distinct from Accrued Liabilities Current because this element includes employee-related liabilities.

No definition available.

Name:	erii_AccruedExpensesAndOtherCurrentLiabilities
Namespace Prefix:	erii_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant