Stock Incentive Plan and Stock-based Compensation - Summary of Changes in SARs Granted (Details) - SARs - $ / shares	9 Months Ended	12 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Awards, Awards outstanding, Beginning balance	49,294
Number of Awards, Awards outstanding, Ending balance	49,294	49,294
Weighted-Average Exercise Price, Awards outstanding, Beginning balance	$ 9.24
Weighted-Average Exercise Price, Awards outstanding, Ending balance	$ 9.24	$ 9.24
Weighted-Average Remaining Contractual Term, Balance	7 years 6 months 14 days	8 years 3 months 14 days

Share based compensation arrangement by share based payment award equity instruments other than options non-vested weighted-average exercise price.

No definition available.

+ Details

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Namespace Prefix:	hrmy_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- 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

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- Details

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