v3.26.3
Financial Instruments - Schedule Of Fair Value Of The Derivative Financial Instruments And A Maturity Analysis Of The Derivatives Cash Flows (Details)
€ in Thousands, £ in Thousands, kr in Thousands
 12 Months Ended
Dec. 31, 2025
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Dec. 31, 2024
USD ($)
Jun. 30, 2026
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Jun. 30, 2026
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Jun. 30, 2026
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Jun. 30, 2026
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€ / $
Dec. 31, 2025
GBP (£)
Dec. 31, 2025
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Dec. 31, 2025
USD ($)
Dec. 31, 2025
$ / kr
Dec. 31, 2025
EUR (€)
Dec. 31, 2025
€ / kr
Dec. 31, 2025
NOK (kr)
Dec. 31, 2025
kr / $
Dec. 31, 2025
£ / $
Dec. 31, 2025
€ / $
Dec. 31, 2024
GBP (£)
Dec. 31, 2024
£ / kr
Dec. 31, 2024
USD ($)
Dec. 31, 2024
$ / kr
Dec. 31, 2024
EUR (€)
Dec. 31, 2024
€ / kr
Dec. 31, 2024
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Dec. 31, 2024
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Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted sales:                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     £ 891             £ 2,076   $ 13,812,000   € 490                          
Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted sales: | 6 months and less                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     891             1,185   13,812,000   490                          
Average forward rate       13.79             13.85   10.58   12.14                        
Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted sales: | 6-12 months                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     0             891   0   0                          
Average forward rate       0             13.79   0   0                        
Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted sales: | 1-2 years                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     0             0   0   0                          
Average forward rate       0             0   0   0                        
Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted purchases:                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     245             940       150                          
Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted purchases: | 6 months and less                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     245             695       150                          
Average forward rate       13.9             13.92       12.03                        
Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted purchases: | 6-12 months                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     0             245       0                          
Average forward rate       0             13.9       0                        
Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted purchases: | 1-2 years                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     0             0       0                          
Average forward rate       0             0       0                        
Foreign exchange forward contracts | Derivative financial instruments—not designated as hedging instruments                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     11,200   € 42,100 kr 69,800       13,800       49,300   kr 131,200                      
Foreign exchange forward contracts | Derivative financial instruments—not designated as hedging instruments | 6 months and less                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     6,100   22,800 28,200       6,000       21,600   97,900                      
Average forward rate             0.1 1.35 1.2               0.1 1.35 1.19                
Foreign exchange forward contracts | Derivative financial instruments—not designated as hedging instruments | 6-12 months                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     5,100   19,300 41,600       5,300       18,900   16,500                      
Average forward rate             0.1 1.35 1.21               0.1 1.35 1.2                
Foreign exchange forward contracts | Derivative financial instruments—not designated as hedging instruments | 1-2 years                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts     £ 0   € 0 kr 0       2,500       8,800   16,800                      
Average forward rate             0 0 0               0.1 1.34 1.21                
HMH Holding BV And Subsidiaries [Member]                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Beginning balance $ (2,250) $ 1,098                                                  
Change in foreign currency risk 3,481,000 (4,314,000)                                                  
Income tax allocated to cash flow hedges (766) 966                                                  
Ending balance $ 465 $ (2,250)                                                  
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted sales:                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   2,076   13,812,000   0   490       £ 6,027   $ 97,710,000   € 40,449   kr 10,109  
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted sales: | 6 months and less                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   1,185   13,812,000   0   490       3,658   74,136,000   28,141   5,485  
Average forward rate                     13.85   10.58   12.14       0   13.94   10.89   11.9   1.08
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted sales: | 6-12 months                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   891   0   0           294   10,817,000   12,308   4,379  
Average forward rate                     13.79   0   0       0   13.91   10.92   11.93   1.08
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted sales: | 1-2 years                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   0   $ 0   0   0       2,075   12,757,000   0   kr 245  
Average forward rate                     0   0   0       0   13.83   10.54   12.09   0
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted purchases:                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   940       0   150       2,596   4,235,000   2,246      
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted purchases: | 6 months and less                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   695       0   150       1,206   3,185,000   2,246      
Average forward rate                     13.92       12.03       0   13.65           11.76
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted purchases: | 6-12 months                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   245       0   0       450   1,050,000   0      
Average forward rate                     13.9       0       0   13.95           11.94
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted purchases: | 1-2 years                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   0       0   0       £ 940   $ 0   € 0      
Average forward rate                     0       0       0   13.92           0
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted purchases: | 6 months and less                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Average forward rate | € / $                                                     1.11
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted purchases: | 6-12 months                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Average forward rate | € / $                                                     0
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—designated as cash flow hedging instruments | Foreign exchange forward contracts to hedge highly probable forecasted purchases: | 1-2 years                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Average forward rate | € / $                                                     0
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—not designated as hedging instruments                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   13,800       49,300   131,200                      
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—not designated as hedging instruments | 6 months and less                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   6,000       21,600   97,900                      
Average forward rate                                 0.1 1.35 1.19                
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—not designated as hedging instruments | 6-12 months                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   5,300       18,900   16,500                      
Average forward rate                                 0.1 1.35 1.2                
HMH Holding BV And Subsidiaries [Member] | Foreign exchange forward contracts | Derivative financial instruments—not designated as hedging instruments | 1-2 years                                                      
Derivative Instruments and Hedging Activities Disclosures [Line Items]                                                      
Notional amounts                   £ 2,500       € 8,800   kr 16,800                      
Average forward rate                                 0.1 1.34 1.21