The extension period for the term of the debt instrument.

No definition available.

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Balance Type:	na
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- Definition

Percentage of the fees associated with providing collateral for the credit facility.

+ References

No definition available.

+ Details

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- 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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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
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Period Type:	duration

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

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Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of the fees associated with providing collateral for the credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

+ Details

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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

+ Details

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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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Period Type:	duration

- Definition

The cash inflow from a borrowing supported by a written promise to pay an obligation.

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Balance Type:	debit
Period Type:	duration

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- Details

Name:	us-gaap_DebtInstrumentAxis=hrth_TexasCapitalFacilityMember
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- Details

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Note F - Long-term Debt (Details Textual) - USD ($) $ in Thousands							3 Months Ended			6 Months Ended
	May 05, 2021	May 11, 2020	Apr. 14, 2020	May 07, 2019	Jan. 09, 2018	Apr. 17, 2017	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Letters of Credit Outstanding, Amount							$ 0			$ 0
Interest Expense, Debt, Total							200		$ 100	300	$ 300
Gain (Loss) on Extinguishment of Debt, Total							10,000		$ (0)	10,000	$ (0)
Standby Letters of Credit [Member]
Long-term Line of Credit, Total							1,100			1,100
Texas Capital Facility [Member]
Long-term Line of Credit, Total							13,100			13,100		$ 17,100
Line of Credit Facility, Remaining Borrowing Capacity							800			$ 800
Texas Capital Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 15,000	$ 19,000			$ 22,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage						0.50%
Line of Credit Facility, Collateral Fees, Percentage						0.50%
Line of Credit Facility, Collateral Fees, Amount								$ 100
Debt Instrument, Term, Extension Period (Year)	1 year	1 year		1 year	1 year
Texas Capital Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate						1.95%
Texas Capital Credit Facility [Member] \| Prime Rate [Member]
Debt Instrument, Basis Spread on Variable Rate						0.75%
Texas Capital Credit Facility [Member] \| Standby Letters of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity						$ 5,000
Texas Capital Credit Facility [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity						$ 20,000
Paycheck Protection Program CARES Act [Member]
Proceeds from Notes Payable, Total			$ 10,000
Gain (Loss) on Extinguishment of Debt, Total							$ 10,000