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Subsequent Events (Details) - ATI Inc. 5.875% Senior Notes due 2027 - Finance leases and other - USD ($) $ in Millions	Jul. 08, 2026	Jun. 28, 2026	Jun. 08, 2026
Subsequent Event [Line Items]
Interest rate		5.875%	5.875%
Subsequent Event
Subsequent Event [Line Items]
Debt extinguishment costs	$ 350.0
Interest rate	5.875%
Write-off of the related unamortized debt issuance costs	$ 1.2