Basis of Presentation (Policies)	3 Months Ended
Dec. 28, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	On November 4, 2024 (the “Closing Date”), Treasure Holdco, Inc. (“Treasure”), which was a wholly owned subsidiary of Berry Global Group, Inc. (“Berry”), completed its merger (the “Transaction”) with the Glatfelter Corporation (“GLT”) which concurrently changed its name to Magnera Corporation (“the Company,” “we,” or “Magnera”). As a result, pre-Transaction Treasure shareholders received shares of Magnera representing 90% of the combined company and GLT shareholders retained 10%. The Company’s shares trade on the New York Stock Exchange under the trading symbol MAGN. The accompanying unaudited Consolidated and Combined Financial Statements of Magnera Corporation have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) pursuant to the rules and regulations of the Securities and Exchange Commission (the "SEC") for interim reporting. Accordingly, they do not include all of the information and footnotes required by GAAP for complete annual financial statements.
Use of Estimates	In preparing financial statements in conformity with GAAP, we must make estimates and assumptions that affect the reported amounts and disclosures at the date of the financial statements and during the reporting period. Actual results could differ from those estimates.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In November 2023, the Financial Accounting Standards Board ("FASB") issued ASU No.2023-07 "Segment Reporting (Topic 280): Improvements to Reporting Segment Disclosures." The ASU was issued to improve reportable segment disclosure requirements, primarily through enhanced disclosures of significant segment expenses that are regularly provided to the chief operating decision maker and included within segment profit and loss. This guidance is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted, and applied retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact of adopting this guidance. In December 2023, the FASB issued ASU No.2023-09 "Income Taxes (Topic 740): Improvements to Income Tax Disclosures." The ASU was issued to improve transparency and disclosure requirements for the rate recognition, income taxes paid and other tax disclosures. The amendments in ASU 2023-09 are effective for fiscal years beginning after December 15, 2024, with early adoption permitted, and may be applied either prospectively or retrospectively. The Company is currently evaluating the impact of adopting this guidance. In November 2024, the FASB issued ASU No.2024-03 “Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses”, which requires an entity to disclose disaggregated information about certain income statement expense line items on the face of the income statement. This guidance is effective for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027, with early adoption permitted, and may be applied either prospectively or retrospectively. The Company is currently evaluating the impact of adopting this guidance.
Revenue Recognition	Revenue is recognized when performance obligations are satisfied, in an amount reflecting the consideration to which the Company expects to be entitled. We consider the promise to transfer products to be our sole performance obligation. Generally, our revenue is recognized for standard promised goods at the time of shipment, when title and risk of loss pass to the customer. The Company disaggregates revenue based on geography.

Basis of Presentation (Policies)

3 Months Ended

Dec. 28, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

On November 4, 2024 (the “Closing Date”), Treasure Holdco, Inc. (“Treasure”), which was a wholly owned subsidiary of Berry Global Group, Inc. (“Berry”), completed its merger (the “Transaction”) with the Glatfelter Corporation (“GLT”) which concurrently changed its name to Magnera Corporation (“the Company,” “we,” or “Magnera”). As a result, pre-Transaction Treasure shareholders received shares of Magnera representing 90% of the combined company and GLT shareholders retained 10%. The Company’s shares trade on the New York Stock Exchange under the trading symbol MAGN.

The accompanying unaudited Consolidated and Combined Financial Statements of Magnera Corporation have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) pursuant to the rules and regulations of the Securities and Exchange Commission (the "SEC") for interim reporting. Accordingly, they do not include all of the information and footnotes required by GAAP for complete annual financial statements.

Use of Estimates

In preparing financial statements in conformity with GAAP, we must make estimates and assumptions that affect the reported amounts and disclosures at the date of the financial statements and during the reporting period. Actual results could differ from those estimates.

Recently Issued Accounting Pronouncements

In November 2023, the Financial Accounting Standards Board ("FASB") issued ASU No.2023-07 "Segment Reporting (Topic 280): Improvements to Reporting Segment Disclosures." The ASU was issued to improve reportable segment disclosure requirements, primarily through enhanced disclosures of significant segment expenses that are regularly provided to the chief operating decision maker and included within segment profit and loss. This guidance is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted, and applied retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact of adopting this guidance.

In December 2023, the FASB issued ASU No.2023-09 "Income Taxes (Topic 740): Improvements to Income Tax Disclosures." The ASU was issued to improve transparency and disclosure requirements for the rate recognition, income taxes paid and other tax disclosures. The amendments in ASU 2023-09 are effective for fiscal years beginning after December 15, 2024, with early adoption permitted, and may be applied either prospectively or retrospectively. The Company is currently evaluating the impact of adopting this guidance.

In November 2024, the FASB issued ASU No.2024-03 “Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses”, which requires an entity to

disclose disaggregated information about certain income statement expense line items on the face of the income statement. This guidance is effective for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027, with early adoption permitted, and may be applied either prospectively or retrospectively. The Company is currently evaluating the impact of adopting this guidance.

Revenue Recognition

Revenue is recognized when performance obligations are satisfied, in an amount reflecting the consideration to which the Company expects to be entitled. We consider the promise to transfer products to be our sole performance obligation. Generally, our revenue is recognized for standard promised goods at the time of shipment, when title and risk of loss pass to the customer. The Company disaggregates revenue based on geography.