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Fair Value Measurements - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
Fair Value Measurements - Narrative (Details) - USD ($)	Mar. 31, 2026	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of long-lived assets to be disposed of		$ 59,000,000	$ 8,000,000	$ 12,000,000
Asset, held-for-sale, not part of disposal group			11,000,000
Impairment of intangible assets, finite-lived		0	0	0
Other asset impairment charges		53,000,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent purchase consideration		6,000,000	20,000,000
Other asset impairment charges		6,000,000
Global Rigid Packaging Solutions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of long-lived assets to be disposed of	$ 6,000,000
Other asset impairment charges		25,000,000
Global Flexible Packaging Solutions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other asset impairment charges		9,000,000	4,000,000
Corporate Segment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other asset impairment charges		19,000,000
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent purchase consideration		6,000,000
Discma AG
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent purchase consideration		12,000,000
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of long-lived assets to be disposed of		6,000,000	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of long-lived assets to be disposed of		$ 53,000,000	$ 8,000,000	$ 12,000,000