Fixed charge coverage ratio reported during the year.

No definition available.

Name:	hdsn_FixedChargesCoverageRatio
Namespace Prefix:	hdsn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the minimum amount from availability.

+ References

No definition available.

+ Details

Name:	hdsn_LineOfCreditFacilityCovenantComplianceMinimumLiquidity
Namespace Prefix:	hdsn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the minimum amount to be derived from availability.

+ References

No definition available.

+ Details

Name:	hdsn_LineOfCreditFacilityCovenantComplianceMinimumLiquidityToBeDerivedFromAvailability
Namespace Prefix:	hdsn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum amount of shares that can be repurchased by the company over the term of credit facility as per the covenant terms mentioned in the amendment.

+ References

No definition available.

+ Details

Name:	hdsn_LineOfCreditFacilityCovenantTermsMaximumShareRepurchaseOverFacilityTermAmount
Namespace Prefix:	hdsn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum amount of shares that can be repurchased by the company per calendar year after first fiscal year following the current fiscal year as per the covenant's terms mentioned in the amendment.

+ References

No definition available.

+ Details

Name:	hdsn_LineOfCreditFacilityCovenantTermsMaximumShareRepurchasePerCalendarYearAfterYearOneAmount
Namespace Prefix:	hdsn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum amount of shares that can be repurchased by the company per calendar year as per the covenant's terms mentioned in the amendment.

+ References

No definition available.

+ Details

Name:	hdsn_LineOfCreditFacilityCovenantTermsMaximumShareRepurchasePerCalendarYearAmount
Namespace Prefix:	hdsn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The minimum aggregate undrawn term loan availability used to determine percentage of excess cash flow to be used to paydown the loan.

+ References

No definition available.

+ Details

Name:	hdsn_MinimumAggregateUndrawnLoanAvailability
Namespace Prefix:	hdsn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the period for FCCR covenant.

+ References

No definition available.

+ Details

Name:	hdsn_PeriodForFixedChargeCoverageRatio
Namespace Prefix:	hdsn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482949/835-30-55-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69B

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69C

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482900/835-30-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477548/944-605-55-15

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477548/944-605-55-12

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
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 the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types: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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

+ 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
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-14

+ Details

Name:	us-gaap_ProceedsFromLinesOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=hdsn_WellsFargoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=hdsn_FCCRMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
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_CreditFacilityAxis=hdsn_FourthAmendmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_StatementScenarioAxis=hdsn_BaseRateLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=hdsn_FedFundsRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_SecuredOvernightFinancingRateSofrMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=hdsn_PrimeCommercialLendingRateOfWellsFargoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=hdsn_SofrLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

Short-term and long-term debt (Details) - USD ($) $ in Thousands	Mar. 22, 2022	Mar. 02, 2022	Mar. 31, 2026	Nov. 25, 2025	Jun. 23, 2025	Oct. 23, 2024	Jun. 06, 2024
Minimum \| Wells Fargo \| FCCR
Short-term and long-term debt
Fixed charges coverage ratio		1
Maximum \| Wells Fargo \| FCCR
Short-term and long-term debt
Fixed charges coverage ratio		1
Revolving Credit Facility \| Wells Fargo \| FCCR
Short-term and long-term debt
Period for FCCR covenant	2 months
Fourth Amendment \| Wells Fargo
Short-term and long-term debt
Stock repurchase amount				$ 5,000
Maximum aggregate shares repurchase amount				$ 20,000
Wells Fargo
Short-term and long-term debt
Amount borrowed		$ 15,000
Maximum borrowing capacity		75,000
Amount outstanding, letters of credit		1,300
Minimum liquidity requirement		5,000
Minimum amount to be derived from availability		3,000
Minimum aggregate undrawn loan availability		$ 11,250
Borrowing capacity			$ 40,000
Debt instrument loan amount			$ 0
Stock repurchase amount						$ 10,000	$ 5,000
Maximum aggregate shares repurchase amount						25,000	$ 15,000
Maximum stock repurchase allowed after first year						$ 5,000
Wells Fargo \| FCCR
Short-term and long-term debt
Period for FCCR covenant		12 months
Wells Fargo \| Minimum
Short-term and long-term debt
Commitment fee percent		0.35%
Wells Fargo \| Maximum
Short-term and long-term debt
Commitment fee percent		0.75%
Wells Fargo \| Base Rate loans \| Base Rate
Short-term and long-term debt
Debt instrument, basis spread on variable rate		1.00%
Wells Fargo \| Base Rate loans \| Federal funds
Short-term and long-term debt
Debt instrument, basis spread on variable rate		0.50%
Wells Fargo \| Base Rate loans \| SOFR
Short-term and long-term debt
Debt instrument, basis spread on variable rate		1.00%
Wells Fargo \| Base Rate loans \| Prime commercial lending rate of Wells Fargo \| Minimum
Short-term and long-term debt
Debt instrument, basis spread on variable rate		1.25%
Wells Fargo \| Base Rate loans \| Prime commercial lending rate of Wells Fargo \| Maximum
Short-term and long-term debt
Debt instrument, basis spread on variable rate		1.75%
Wells Fargo \| SOFR loans \| SOFR \| Minimum
Short-term and long-term debt
Debt instrument, basis spread on variable rate		2.36%
Wells Fargo \| SOFR loans \| SOFR \| Maximum
Short-term and long-term debt
Debt instrument, basis spread on variable rate		2.86%
Wells Fargo \| Swing line loans
Short-term and long-term debt
Maximum borrowing capacity		$ 9,000
Wells Fargo \| Letters of credit
Short-term and long-term debt
Maximum borrowing capacity		2,000			$ 1,500
Wells Fargo \| Third Amendment
Short-term and long-term debt
Maximum borrowing capacity		$ 75,000			$ 40,000