Financial Instruments and Financial Risk Management - Schedule of Fair Value and Fair Value Hierarchy of Loans and Borrowings Carried at Amortized Cost (Details) - Level 2 - EUR (€) € in Thousands	Jun. 30, 2026	Sep. 30, 2025
Term Loan \| EUR
Disclosure of fair value measurement of liabilities [line items]
Nominal value	€ 375,000	€ 375,000
Term Loan \| USD
Disclosure of fair value measurement of liabilities [line items]
Nominal value	102,934	103,731
Vendor Loan
Disclosure of fair value measurement of liabilities [line items]
Nominal value	226,908	217,408
New Senior Notes
Disclosure of fair value measurement of liabilities [line items]
Nominal value	900,000
Revolving Credit Facility
Disclosure of fair value measurement of liabilities [line items]
Nominal value	80,000
Original Senior Notes
Disclosure of fair value measurement of liabilities [line items]
Nominal value		428,500
Carrying Value \| Term Loan \| EUR
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings	375,646	375,112
Carrying Value \| Term Loan \| USD
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings	102,931	103,677
Carrying Value \| Vendor Loan
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings	228,565	221,391
Carrying Value \| New Senior Notes
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings	900,159
Carrying Value \| Revolving Credit Facility
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings	80,109
Carrying Value \| Original Senior Notes
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings		444,963
Fair Value \| Term Loan \| EUR
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings	391,588	387,500
Fair Value \| Term Loan \| USD
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings	106,873	107,246
Fair Value \| Vendor Loan
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings	236,121	230,176
Fair Value \| New Senior Notes
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings	929,668
Fair Value \| Revolving Credit Facility
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings	€ 80,109
Fair Value \| Original Senior Notes
Disclosure of fair value measurement of liabilities [line items]
Loans and borrowings		€ 450,961

The amount of outstanding funds that the entity is obligated to repay.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 55
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-URIDate 2025-03-27

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- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

+ References

No definition available.

+ Details

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- Definition

The nominal or face amount of a financial instrument, used to calculate payments made on that instrument.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 112
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_112_c&doctype=Standard
-URIDate 2025-03-27

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