Note A - Overview and Significant Accounting Policies (Details Textual) $ in Millions		6 Months Ended
Jan. 30, 2018 USD ($) shares	Jun. 30, 2020
Number of Reportable Segments		1
Founder of Snap Kitchen [Member]
Related Party, Ownership Percentage		9.00%
Securities Purchase Agreement [Member] \| Series A Preferred Stock [Member] \| Wipro [Member]
Sale of Stock, Number of Shares Issued in Transaction (in shares) \| shares	9,926
Convertible Preferred Stock, Shares Issued upon Conversion as Percent of Common Stock Outstanding	16.00%
Sale of Stock, Consideration Received on Transaction \| $	$ 9.9

Represents shares issued upon conversion as percentage of common stock outstanding for convertible preferred stock.

No definition available.

Name:	hrth_ConvertiblePreferredStockSharesIssuedUponConversionAsPercentOfCommonStockOutstanding
Namespace Prefix:	hrth_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The ownership percentage of the related party in the company.

+ References

No definition available.

+ Details

Name:	hrth_RelatedPartyOwnershipPercentage
Namespace Prefix:	hrth_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash received on stock transaction after deduction of issuance costs.

+ References

No definition available.

+ Details

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

- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=hrth_FounderOfSnapKitchenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=hrth_SecuritiesPurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_SeriesAPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=hrth_WiproMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: