Pensions and Other Postretirement Benefits - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Company's contributions to its pension plans	$ 2,000,000	$ 2,000,000
Pension Benefits \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Expected contributions	10,000,000
Pension Benefits \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Expected contributions	15,000,000
Postretirement Health Coverage
Defined Benefit Plan Disclosure [Line Items]
Company's contributions to its pension plans	0	$ 0
Expected contributions	$ 2,000,000

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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+ Details

- 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.

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+ Details

GRAPHIC PACKAGING HOLDING CO 10-Q