XML 56 R30.htm IDEA: XBRL DOCUMENT
v3.25.4

Investments and Fair Value Measurements (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2025
Investments, Fair Value Disclosure [Abstract] |
Schedule of Amortized Cost and Fair Value of Available for Sale Securities | The following table presents the Company’s financial assets measured on a recurring basis by contractual maturity, including pricing category, amortized cost and fair value. Gross unrealized gains and losses were not material for the periods presented. As of December 31, 2025 and December 31, 2024, the Company had no financial liabilities and no Level 3 financial assets.
|  |  | December 31, 2025 |  | December 31, 2024
| Pricing Category |  | Amortized Cost |  | Fair Value |  | Amortized Cost |  | Fair Value
|  |  | (In thousands)
Cash equivalents |  |  |  |  |  |  |  |
Money market securities | Level 1 |  | $11,225 |  | $11,225 |  | $2,580 |  | $2,580
U.S. treasury securities | Level 2 |  | 12,952 |  | 12,955 |  | — |  | —
Total cash equivalents |  | 24,177 |  | 24,180 |  | 2,580 |  | 2,580
Short-term investments |  |  |  |  |  |  |  |
U.S. treasury securities | Level 2 |  | 13,618 |  | 13,640 |  | 20,303 |  | 20,345
Corporate notes and bonds | Level 2 |  | 13,505 |  | 13,533 |  | 27,995 |  | 28,047
Total short-term investments |  | 27,123 |  | 27,173 |  | 48,298 |  | 48,392
Long-term investments |  |  |  |  |  |  |  |
U.S. treasury securities | Level 2 |  | 1,959 |  | 1,971 |  | 999 |  | 1,000
Corporate notes and bonds | Level 2 |  | 6,038 |  | 6,063 |  | 18,983 |  | 19,035
Municipal and agency notes and bonds | Level 2 |  | — |  | — |  | 1,799 |  | 1,797
Total long-term investments |  | 7,997 |  | 8,034 |  | 21,781 |  | 21,832
Total short and long-term investments |  | 35,120 |  | 35,207 |  | 70,079 |  | 70,224
Total |  | $59,297 |  | $59,387 |  | $72,659 |  | $72,804
Schedule of Sales of Available-for-Sale Investments | The following table presents the sales of available-for-sale investments.
| Years Ended December 31,
| 2025 |  | 2024 |  | 2023
(In thousands) |
Corporate notes and bonds | $— |  | $— |  | $2,966

X
- Definition Debt Securities, Available-For-Sale, Proceeds From Sale [Table Text Block] + References No definition available. + Details
Name: | erii_DebtSecuritiesAvailableForSaleProceedsFromSaleTableTextBlock
Namespace Prefix: | erii_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule Of Amortized Cost And Fair Value Of Available For Sale Securities [Table Text Block] + References No definition available. + Details
Name: | erii_ScheduleOfAmortizedCostAndFairValueOfAvailableForSaleSecuritiesTableTextBlock
Namespace Prefix: | erii_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

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