Debt Instrument, Renewal Term

No definition available.

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- Definition

Line Of Credit Facility, Accordion Feature, Increase Limit

+ References

No definition available.

+ Details

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Namespace Prefix:	hrth_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

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+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Period between issuance and maturity of debt instrument, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

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+ Details

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

- 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

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+ Details

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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://www.xbrl.org/2009/role/commonPracticeRef
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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

+ Details

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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 available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- 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
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Balance Type:	debit
Period Type:	duration

- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ References

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- Details

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Period Type:

- Details

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Period Type:

- Details

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- Details

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Debt - Credit Facility (Details) - USD ($) $ in Thousands			6 Months Ended
Debt - Credit Facility (Details) - USD ($) $ in Thousands	Jun. 24, 2025	Dec. 21, 2021	Jun. 30, 2026	Dec. 31, 2025
Line of Credit Facility [Line Items]
Letter of credit outstanding			$ 700	$ 700
Amount drawn on letters of credit			0
Short-term debt			$ 3,000	0
Texas Capital Bank
Line of Credit Facility [Line Items]
Interest rate			5.99%
Unused commitment fee rate			0.25%
Revolving Credit Facility \| Texas Capital Bank
Line of Credit Facility [Line Items]
Margin per annum		2.25%
Short-term debt			$ 3,000
Credit Facility \| Revolving Credit Facility \| Texas Capital Bank
Line of Credit Facility [Line Items]
Term (in years)		3 years
Maximum borrowing capacity		$ 25,000
Credit Facility \| Letter of Credit \| Texas Capital Bank
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 3,000
New Credit Facility
Line of Credit Facility [Line Items]
Additional borrowing capacity			$ 21,300	24,300
New Credit Facility \| Revolving Credit Facility \| Texas Capital Bank
Line of Credit Facility [Line Items]
Renewal term (in months)	3 years
Increase in commitments	$ 10,000
Short-term debt				$ 0