Summary of significant accounting policies (Policies)	6 Months Ended	12 Months Ended
Jun. 30, 2026	Dec. 31, 2025
Accounting Policies [Line Items]
Offering Costs	Offering costs In connection with our IPO, HMH B.V. and its affiliates incurred accounting, legal and other costs, which were reimbursed by us. Such costs were recorded as a reduction to equity against the proceeds from the IPO. Deferred offering costs of $21.3 million and $26.2 million were recognized in prepaids and other current assets in our condensed consolidated balance sheets as of December 31, 2025 and at the IPO date of April 2, 2026, respectively.
HMH Holding Inc. [Member]
Accounting Policies [Line Items]
Basis of Presentation		Basis of presentation The Company’s balance sheets have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”). As there has been no operating activity for this entity since its inception, separate statements of income and comprehensive income, cash flows and changes in stockholder’s equity have not been presented. The Company’s year-end is December 31. Summary of significant accounting policies The preparation of financial statements in accordance with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities, related revenues and expenses and the disclosure of gain and loss contingencies at the date of the financial statements and during the periods presented. The Company bases these estimates on historical results and various other assumptions believed to be reasonable, all of which form the basis for making estimates concerning the carrying values of assets and liabilities that are not readily available from other sources. Actual results could differ materially from those estimates.
Offering Costs		Offering costs In connection with the Company’s initial public offering, affiliates of the Company have or will incur accounting, legal and other costs, which will be reimbursed by the Company upon consummation of the initial public offering. Such costs will be deferred and recorded as a reduction to stockholder’s equity and recorded against the proceeds from the offering. In the event the offering is aborted, such deferred offering costs will be expensed.
Organization costs		Organization costs Organization costs will be expensed as incurred. Such costs are comprised of the legal and professional fees associated with the formation of the Company.

Summary of significant accounting policies (Policies)

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Offering costs

In connection with our IPO, HMH B.V. and its affiliates incurred accounting, legal and other costs, which were reimbursed by us. Such costs were recorded as a reduction to equity against the proceeds from the IPO. Deferred offering costs of $21.3 million and $26.2 million were recognized in prepaids and other current assets in our condensed consolidated balance sheets as of December 31, 2025 and at the IPO date of April 2, 2026, respectively.

HMH Holding Inc. [Member]

Accounting Policies [Line Items]

Basis of Presentation

Basis of presentation

The Company’s balance sheets have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”). As there has been no operating activity for this entity since its inception, separate statements of income and comprehensive income, cash flows and changes in stockholder’s equity have not been presented. The Company’s year-end is December 31.

Summary of significant accounting policies

The preparation of financial statements in accordance with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities, related revenues and expenses and the disclosure of gain and loss contingencies at the date of the financial statements and during the periods presented. The Company bases these estimates on historical results and various other assumptions believed to be reasonable, all of which form the basis for making estimates concerning the carrying values of assets and liabilities that are not readily available from other sources. Actual results could differ materially from those estimates.

Offering Costs

Offering costs

In connection with the Company’s initial public offering, affiliates of the Company have or will incur accounting, legal and other costs, which will be reimbursed by the Company upon consummation of the initial public offering. Such costs will be deferred and recorded as a reduction to stockholder’s equity and recorded against the proceeds from the offering. In the event the offering is aborted, such deferred offering costs will be expensed.

Organization costs

Organization costs will be expensed as incurred. Such costs are comprised of the legal and professional fees associated with the formation of the Company.