XML 47 R37.htm IDEA: XBRL DOCUMENT
v3.22.2.2

Schedule of Investments and Unrealized Gains/Losses (Details) $ in Thousands | 6 Months Ended
--- | ---
Oct. 31, 2022 USD ($)
Net Investment Income [Line Items] |
Total Cost | $ 35,868
Unrealized Gains (Losses) | (28)
Market Value | 35,840
Corporate Bonds [Member] |
Net Investment Income [Line Items] |
Total Cost | 27,364
Unrealized Gains (Losses) | (23)
Market Value | 27,341
Government Bonds and Notes [Member] |
Net Investment Income [Line Items] |
Total Cost | 5,008
Unrealized Gains (Losses) |
Market Value | 5,008
Government Agency [Member] |
Net Investment Income [Line Items] |
Total Cost | 3,496
Unrealized Gains (Losses) | (5)
Market Value | $ 3,491

X
- Definition Cost of the investment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 210 -Section 50 -Paragraph 6 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=99383244&loc=d3e12121-115841 + Details
Name: | us-gaap_InvestmentOwnedAtCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months. + References No definition available. + Details
Name: | us-gaap_MoneyMarketFundsAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- 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_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of unrealized gain (loss) on investment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585 + Details
Name: | us-gaap_UnrealizedGainLossOnInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_InvestmentTypeAxis=OPTT_CorporateBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=OPTT_GovernmentBondsandNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=OPTT_GovernmentAgencyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |