$ATI
ATI INC Stock $ati

$ati Overview Financials Valuation SEC Filings Company Website

2024 Q4 Form 10-Q Financial Statement

#000162828024044066 Filed on October 29, 2024

Income Statement

Concept	2024 Q4	2024 Q3	2023 Q4
Revenue		$1.051B	$1.064B
YoY Change		2.5%	5.3%
Cost Of Revenue		$826.4M	$858.3M
YoY Change		-0.55%	4.07%
Gross Profit		$224.8M	$205.7M
YoY Change		15.52%	10.77%
Gross Profit Margin		21.39%	19.33%
Selling, General & Admin		$82.40M	$92.30M
YoY Change		18.05%	20.18%
% of Gross Profit		36.65%	44.87%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization		$38.50M	$39.50M
YoY Change		8.15%	10.34%
% of Gross Profit		17.13%	19.2%
Operating Expenses		$82.40M	$92.30M
YoY Change		18.05%	20.18%
Operating Profit		$142.2M	$113.4M
YoY Change		13.58%	4.13%
Interest Expense		-$28.20M	-$27.80M
YoY Change		15.1%	52.75%
% of Operating Profit		-19.83%	-24.51%
Other Income/Expense, Net		$4.400M	-$72.40M
YoY Change			1127.12%
Pretax Income		$114.9M	$8.100M
YoY Change		35.98%	-90.52%
Income Tax		$28.30M	-$141.1M
% Of Pretax Income		24.63%	-1741.98%
Net Earnings		$82.70M	$145.7M
YoY Change		9.25%	89.47%
Net Earnings / Revenue		7.87%	13.69%
Basic Earnings Per Share		$0.64	$1.15
Diluted Earnings Per Share		$0.57	$0.99
COMMON SHARES
Basic Shares Outstanding	142.6M shares	124.5M shares	127.6M shares
Diluted Shares Outstanding		146.8M shares	150.2M shares

Balance Sheet

Concept	2024 Q3	2023 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments	$406.6M	$743.9M
YoY Change	-6.08%	27.38%
Cash & Equivalents	$406.6M	$743.9M
Short-Term Investments
Other Short-Term Assets	$136.6M	$62.20M
YoY Change	86.36%	16.48%
Inventory	$1.415B	$1.248B
Prepaid Expenses
Receivables	$730.2M	$684.1M
Other Receivables	$0.00	$0.00
Total Short-Term Assets	$2.778B	$2.738B
YoY Change	6.87%	10.55%
LONG-TERM ASSETS
Property, Plant & Equipment	$1.747B	$1.666B
YoY Change	7.39%	7.54%
Goodwill	$227.2M	$227.2M
YoY Change	0.0%	0.0%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets	$313.7M	$354.3M
YoY Change	12.88%	83.67%
Total Long-Term Assets	$2.287B	$2.247B
YoY Change	7.32%	14.13%
TOTAL ASSETS
Total Short-Term Assets	$2.778B	$2.738B
Total Long-Term Assets	$2.287B	$2.247B
Total Assets	$5.066B	$4.985B
YoY Change	7.07%	12.14%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$528.5M	$524.8M
YoY Change	21.49%	-5.15%
Accrued Expenses	$242.4M	$256.8M
YoY Change	-1.7%	16.83%
Deferred Revenue	$146.5M	$163.6M
YoY Change	32.94%	9.73%
Short-Term Debt	$0.00	$0.00
YoY Change
Long-Term Debt Due	$27.90M	$31.90M
YoY Change	-25.6%	-23.5%
Total Short-Term Liabilities	$945.3M	$977.1M
YoY Change	13.99%	1.37%
LONG-TERM LIABILITIES
Long-Term Debt	$1.856B	$2.148B
YoY Change	-13.61%	25.87%
Other Long-Term Liabilities	$152.1M	$379.8M
YoY Change	-17.92%	82.86%
Total Long-Term Liabilities	$152.1M	$2.528B
YoY Change	-17.92%	1116.9%
TOTAL LIABILITIES
Total Short-Term Liabilities	$945.3M	$977.1M
Total Long-Term Liabilities	$152.1M	$2.528B
Total Liabilities	$3.154B	$3.612B
YoY Change	-6.56%	9.84%
SHAREHOLDERS EQUITY
Retained Earnings	-$72.80M	-$70.10M
YoY Change	-118.26%	-139.63%
Common Stock	$1.952B	$1.710B
YoY Change	14.65%	1.73%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$13.30M	$184.0M
YoY Change	-91.34%	111.49%
Treasury Stock Shares
Shareholders Equity	$1.791B	$1.373B
YoY Change
Total Liabilities & Shareholders Equity	$5.066B	$4.985B
YoY Change	7.07%	12.14%

Cashflow Statement

Concept	2024 Q3	2023 Q4
OPERATING ACTIVITIES
Net Income	$82.70M	$145.7M
YoY Change	9.25%	89.47%
Depreciation, Depletion And Amortization	$38.50M	$39.50M
YoY Change	8.15%	10.34%
Cash From Operating Activities	$14.40M	$417.2M
YoY Change	-112.61%	28.65%
INVESTING ACTIVITIES
Capital Expenditures	$65.80M	$53.40M
YoY Change	49.55%	75.66%
Acquisitions
YoY Change
Other Investing Activities	$4.700M	$3.400M
YoY Change	193.75%	-27.66%
Cash From Investing Activities	-$61.10M	-$50.00M
YoY Change	44.1%	94.55%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	27.70M	-56.20M
YoY Change	-91.41%	28.6%
NET CHANGE
Cash From Operating Activities	14.40M	417.2M
Cash From Investing Activities	-61.10M	-50.00M
Cash From Financing Activities	27.70M	-56.20M
Net Change In Cash	-19.00M	311.0M
YoY Change	-111.46%	22.01%
FREE CASH FLOW
Cash From Operating Activities	$14.40M	$417.2M
Capital Expenditures	$65.80M	$53.40M
Free Cash Flow	-$51.40M	$363.8M
YoY Change	-67.51%	23.78%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
	dei	Document Type DocumentType	10-Q
	dei	Amendment Flag AmendmentFlag	false
	dei	Entity Central Index Key EntityCentralIndexKey	0001018963
	dei	Document Period End Date DocumentPeriodEndDate	2024-09-29
	dei	Document Transition Report DocumentTransitionReport	false
	dei	Entity File Number EntityFileNumber	1-12001
	dei	Entity Registrant Name EntityRegistrantName	ATI Inc.
	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	25-1792394
	dei	Entity Address City Or Town EntityAddressCityOrTown	Dallas,
	dei	Entity Address State Or Province EntityAddressStateOrProvince	TX
	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	75201
	dei	City Area Code CityAreaCode	800
	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
	dei	Entity Small Business EntitySmallBusiness	false
	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
	dei	Entity Shell Company EntityShellCompany	false
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CY2023Q4	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	-1800000	usd
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	-8000000.0	usd
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	-100000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	0	usd
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	1700000	usd
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	0	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-1400000	usd
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	2000000.0	usd
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-20500000	usd
	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	-400000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	0	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-800000	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	0	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-4100000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-9200000	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	11800000	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-30400000	usd
CY2023Q4	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	84900000	usd
	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	252400000	usd
	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	243800000	usd
CY2023Q4	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	1800000	usd
	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	13100000	usd
	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	5700000	usd
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	239300000	usd
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	238100000	usd
	us-gaap	Profit Loss ProfitLoss	274200000	usd
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	106600000	usd
	us-gaap	Share Based Compensation ShareBasedCompensation	21500000	usd
	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	2200000	usd
	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	100000	usd
	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	-600000	usd
	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	158200000	usd
	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	104000000.0	usd
	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	-108200000	usd
	ati	Pension Plan Contributions PensionPlanContributions	-272000000.0	usd
	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	-12300000	usd
	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	81600000	usd
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	-331300000	usd
	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	147300000	usd
	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	3300000	usd
	ati	Transaction Costs For Sales Of Businesses Net Of Proceeds TransactionCostsForSalesOfBusinessesNetOfProceeds	-300000	usd
	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-1100000	usd
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-143200000	usd
CY2023Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1355900000	usd
	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-29
	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2024
	dei	Document Quarterly Report DocumentQuarterlyReport	true
	dei	Entity Address Address Line1 EntityAddressAddressLine1	2021 McKinney Avenue
	dei	Local Phone Number LocalPhoneNumber	289-7454
	dei	Security12b Title Security12bTitle	Common stock, par value $0.10
	dei	Trading Symbol TradingSymbol	ATI
	dei	Security Exchange Name SecurityExchangeName	NYSE
CY2024Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1746500000	usd
CY2024Q3	us-gaap	Goodwill Goodwill	227200000	usd
CY2023Q4	us-gaap	Goodwill Goodwill	227200000	usd
CY2024Q3	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	1855500000	usd
CY2023Q4	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-500000	usd
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-1200000	usd
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	2200000	usd
CY2024Q3	ati	Gain Loss On Asset And Business Sales Net GainLossOnAssetAndBusinessSalesNet	300000	usd
CY2023Q4	ati	Gain Loss On Asset And Business Sales Net GainLossOnAssetAndBusinessSalesNet	-100000	usd
	ati	Nonoperatingretirementbenefitexpense Nonoperatingretirementbenefitexpense	11100000	usd
	ati	Interest Expense Net InterestExpenseNet	65000000.0	usd
CY2024Q3	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	4400000	usd
	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	5200000	usd
	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	1300000	usd
CY2023Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	99000000.0	usd
CY2023Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4900000	usd
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	70500000	usd
CY2024Q3	us-gaap	Assets Current AssetsCurrent	2778400000	usd
CY2024Q3	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	313700000	usd
CY2023Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	2147700000	usd
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3109700000	usd
	us-gaap	Gross Profit GrossProfit	649600000	usd
	us-gaap	Gross Profit GrossProfit	596900000	usd
CY2024Q3	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	500000	usd
CY2024Q3	ati	Gain Loss On Asset And Business Sales Net GainLossOnAssetAndBusinessSalesNet	300000	usd
CY2023Q4	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	0	usd
CY2024Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	114900000	usd
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	311100000	usd
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	287100000	usd
CY2024Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	28300000	usd
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12900000	usd
	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax	-14000000.0	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	-1900000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	-3700000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	500000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	1300000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-1300000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	-100000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-300000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-900000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1400000	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-2700000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	19600000	usd
CY2024Q3	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	106200000	usd
CY2024Q3	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	7900000	usd
CY2024Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	98300000	usd
	us-gaap	Profit Loss ProfitLoss	240600000	usd
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	112400000	usd
	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	6000000.0	usd
	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	0	usd
	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	198400000	usd
	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	111300000	usd
	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	20200000	usd
	ati	Pension Plan Contributions PensionPlanContributions	0	usd
	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	-7900000	usd
	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	106400000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax	-9200000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	-1900000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	-3700000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	500000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	1300000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-1300000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-1500000	usd
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-3900000	usd
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-4500000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	-100000	usd
	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	-400000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-300000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-900000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	19600000	usd
CY2024Q3	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	106200000	usd
CY2024Q3	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	7900000	usd
CY2024Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	98300000	usd
CY2023Q4	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	83100000	usd
	us-gaap	Profit Loss ProfitLoss	240600000	usd
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	112400000	usd
	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	6000000.0	usd
	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	0	usd
	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	198400000	usd
	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	111300000	usd
	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	20200000	usd
	ati	Pension Plan Contributions PensionPlanContributions	0	usd
	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	-7900000	usd
	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	106400000	usd
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	26300000	usd
	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	191800000	usd
	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	10600000	usd
	ati	Transaction Costs For Sales Of Businesses Net Of Proceeds TransactionCostsForSalesOfBusinessesNetOfProceeds	0	usd
	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-3000000.0	usd
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-178200000	usd
	us-gaap	Proceeds From Issuance Of Debt ProceedsFromIssuanceOfDebt	0	usd
	us-gaap	Proceeds From Issuance Of Debt ProceedsFromIssuanceOfDebt	425000000.0	usd
	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	-7300000	usd
	ati	Receipt Of Convertible Note Capped Call ReceiptOfConvertibleNoteCappedCall	76100000	usd
	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	0	usd
	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	6100000	usd
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	190000000.0	usd
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	55100000	usd
	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	25300000	usd
	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	11100000	usd
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-166200000	usd
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	323400000	usd
	ati	Cash Held For Sale CashHeldForSale	-19200000	usd
	ati	Cash Held For Sale CashHeldForSale	0	usd
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Disposal Group Including Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectDisposalGroupIncludingDiscontinuedOperations	-337300000	usd
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Disposal Group Including Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectDisposalGroupIncludingDiscontinuedOperations	-151100000	usd
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	743900000	usd
CY2023Q1	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	584000000.0	usd
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	26300000	usd
	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	191800000	usd
	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	10600000	usd
	ati	Transaction Costs For Sales Of Businesses Net Of Proceeds TransactionCostsForSalesOfBusinessesNetOfProceeds	0	usd
	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-3000000.0	usd
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-178200000	usd
	us-gaap	Proceeds From Issuance Of Debt ProceedsFromIssuanceOfDebt	0	usd
	us-gaap	Proceeds From Issuance Of Debt ProceedsFromIssuanceOfDebt	425000000.0	usd
	us-gaap	Repayments Of Long Term Debt And Capital Securities RepaymentsOfLongTermDebtAndCapitalSecurities	21900000	usd
	us-gaap	Repayments Of Long Term Debt And Capital Securities RepaymentsOfLongTermDebtAndCapitalSecurities	22000000.0	usd
	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	-5100000	usd
	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	-7300000	usd
	ati	Receipt Of Convertible Note Capped Call ReceiptOfConvertibleNoteCappedCall	76100000	usd
	ati	Receipt Of Convertible Note Capped Call ReceiptOfConvertibleNoteCappedCall	0	usd
	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	0	usd
	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	6100000	usd
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	190000000.0	usd
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	55100000	usd
	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	25300000	usd
	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	11100000	usd
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-166200000	usd
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	323400000	usd
	ati	Cash Held For Sale CashHeldForSale	-19200000	usd
	ati	Cash Held For Sale CashHeldForSale	0	usd
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Disposal Group Including Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectDisposalGroupIncludingDiscontinuedOperations	-337300000	usd
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Disposal Group Including Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectDisposalGroupIncludingDiscontinuedOperations	-151100000	usd
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	743900000	usd
CY2023Q1	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	584000000.0	usd
CY2024Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	406600000	usd
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	432900000	usd
CY2023Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1309200000	usd
CY2023Q4	us-gaap	Profit Loss ProfitLoss	94100000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-9200000	usd
CY2023Q4	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	45400000	usd
CY2023Q4	ati	Employee Stock Plans EmployeeStockPlans	-7200000	usd
CY2024Q2	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1467900000	usd
CY2024Q3	us-gaap	Profit Loss ProfitLoss	86600000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	19600000	usd
CY2024Q3	us-gaap	Stock Issued During Period Value Conversion Of Convertible Securities Net Of Adjustments StockIssuedDuringPeriodValueConversionOfConvertibleSecuritiesNetOfAdjustments	291700000	usd
CY2024Q3	ati	Adjustments To Additional Paid In Capital Convertible Note Capped Call AdjustmentsToAdditionalPaidInCapitalConvertibleNoteCappedCall	76100000	usd
CY2024Q3	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	38800000	usd
CY2023Q1	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1157200000	usd
	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	55500000	usd
	ati	Employee Stock Plans EmployeeStockPlans	-10400000	usd
CY2023Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1355900000	usd
CY2023Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1480500000	usd
	us-gaap	Profit Loss ProfitLoss	240600000	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	11800000	usd
	us-gaap	Stock Issued During Period Value Conversion Of Convertible Securities Net Of Adjustments StockIssuedDuringPeriodValueConversionOfConvertibleSecuritiesNetOfAdjustments	291700000	usd
	ati	Employee Stock Plans EmployeeStockPlans	-1300000	usd
CY2024Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1912000000	usd
CY2024Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	406600000	usd
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	432900000	usd
CY2023Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1309200000	usd
CY2023Q4	us-gaap	Profit Loss ProfitLoss	94100000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-9200000	usd
CY2023Q4	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	45400000	usd
CY2023Q4	ati	Employee Stock Plans EmployeeStockPlans	-7200000	usd
CY2024Q2	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1467900000	usd
CY2024Q3	us-gaap	Profit Loss ProfitLoss	86600000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	19600000	usd
CY2024Q3	us-gaap	Stock Issued During Period Value Conversion Of Convertible Securities Net Of Adjustments StockIssuedDuringPeriodValueConversionOfConvertibleSecuritiesNetOfAdjustments	291700000	usd
CY2024Q3	ati	Adjustments To Additional Paid In Capital Convertible Note Capped Call AdjustmentsToAdditionalPaidInCapitalConvertibleNoteCappedCall	76100000	usd
CY2024Q3	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	38800000	usd
	ati	Employee Stock Plans EmployeeStockPlans	-10400000	usd
CY2023Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1355900000	usd
CY2023Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1480500000	usd
	us-gaap	Profit Loss ProfitLoss	240600000	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	11800000	usd
	us-gaap	Stock Issued During Period Value Conversion Of Convertible Securities Net Of Adjustments StockIssuedDuringPeriodValueConversionOfConvertibleSecuritiesNetOfAdjustments	291700000	usd
	ati	Adjustments To Additional Paid In Capital Convertible Note Capped Call AdjustmentsToAdditionalPaidInCapitalConvertibleNoteCappedCall	76100000	usd
	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	190000000.0	usd
	ati	Employee Stock Plans EmployeeStockPlans	-1300000	usd
CY2024Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1912000000	usd
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2024Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1051200000	usd
CY2023Q4	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1025600000	usd
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3189400000	usd
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3109700000	usd
CY2024Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1051200000	usd
CY2023Q4	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1025600000	usd
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3189400000	usd
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3109700000	usd
CY2024Q3	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
CY2023Q4	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
CY2023Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	3600000000	usd
CY2024Q3	ati	Revenue Remaining Performance Obligation Current RevenueRemainingPerformanceObligationCurrent	0.65	usd
CY2024Q3	ati	Accountsreceivablewithcustomers Accountsreceivablewithcustomers	732800000	usd
CY2023Q4	ati	Accountsreceivablewithcustomers Accountsreceivablewithcustomers	628200000	usd
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2024Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1051200000	usd
CY2023Q4	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1025600000	usd
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3189400000	usd
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3109700000	usd
CY2024Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1051200000	usd
CY2023Q4	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1025600000	usd
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3189400000	usd
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3109700000	usd
CY2024Q3	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
CY2023Q4	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
CY2024Q3	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	3900000000	usd
CY2023Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	3600000000	usd
CY2024Q3	ati	Revenue Remaining Performance Obligation Current RevenueRemainingPerformanceObligationCurrent	0.65	usd
CY2023Q4	ati	Accountsreceivablewithcustomers Accountsreceivablewithcustomers	628200000	usd
CY2023Q1	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	7700000	usd
	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	200000	usd
CY2023Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	3700000	usd
CY2023Q1	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	64100000	usd
	ati	Contractwith Customer Asset Current Period Increase ContractwithCustomerAssetCurrentPeriodIncrease	68900000	usd
	ati	Contractwith Customer Asset Current Period Increase ContractwithCustomerAssetCurrentPeriodIncrease	66600000	usd
CY2024Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	90500000	usd
CY2023Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	163600000	usd
	ati	Contractwith Customer Liability Current Period Increase ContractwithCustomerLiabilityCurrentPeriodIncrease	75100000	usd
	ati	Contractwith Customer Liability Current Reclassifiedto Revenue ContractwithCustomerLiabilityCurrentReclassifiedtoRevenue	-67700000	usd
	ati	Contractwith Customer Liability Current Revenue Recognized ContractwithCustomerLiabilityCurrentRevenueRecognized	-36900000	usd
	ati	Contractwith Customer Liability Current Other ContractwithCustomerLiabilityCurrentOther	0	usd
	ati	Contractwith Customer Liability Current Reclassification ContractwithCustomerLiabilityCurrentReclassification	-12400000	usd
CY2024Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	146500000	usd
CY2023Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	39400000	usd
CY2023Q1	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	7700000	usd
	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	200000	usd
	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	4200000	usd
CY2023Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	3700000	usd
CY2023Q1	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	64100000	usd
	ati	Contractwith Customer Asset Current Period Increase ContractwithCustomerAssetCurrentPeriodIncrease	66600000	usd
	ati	Contractwith Customer Asset Current Reclassifiedto Receivable ContractwithCustomerAssetCurrentReclassifiedtoReceivable	74100000	usd
CY2024Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	90500000	usd
CY2023Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	163600000	usd
	ati	Contractwith Customer Liability Current Period Increase ContractwithCustomerLiabilityCurrentPeriodIncrease	75100000	usd
	ati	Contractwith Customer Liability Current Reclassifiedto Revenue ContractwithCustomerLiabilityCurrentReclassifiedtoRevenue	-67700000	usd
	ati	Contractwith Customer Liability Current Revenue Recognized ContractwithCustomerLiabilityCurrentRevenueRecognized	-36900000	usd
	ati	Contractwith Customer Liability Current Other ContractwithCustomerLiabilityCurrentOther	0	usd
	ati	Contractwith Customer Liability Current Reclassification ContractwithCustomerLiabilityCurrentReclassification	-12400000	usd
CY2024Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	146500000	usd
CY2023Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	39400000	usd
	ati	Contractwith Customer Liability Noncurrent Period Increase ContractwithCustomerLiabilityNoncurrentPeriodIncrease	10800000	usd
	ati	Contractwith Customer Liability Noncurrent Reclassification ContractwithCustomerLiabilityNoncurrentReclassification	12400000	usd
CY2024Q3	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	37800000	usd
CY2024Q3	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	9800000	usd
CY2023Q4	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	8100000	usd
CY2024Q3	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	200000	usd
	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	800000	usd
	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	900000	usd
CY2024Q3	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	217000000.0	usd
CY2024Q3	us-gaap	Inventory Work In Process InventoryWorkInProcess	1188200000	usd
CY2024Q3	us-gaap	Inventory Finished Goods InventoryFinishedGoods	81000000.0	usd
CY2024Q3	us-gaap	Inventory Gross InventoryGross	1486200000	usd
CY2024Q3	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	71700000	usd
	ati	Contractwith Customer Liability Noncurrent Period Increase ContractwithCustomerLiabilityNoncurrentPeriodIncrease	10800000	usd
	ati	Contractwith Customer Liability Noncurrent Reclassification ContractwithCustomerLiabilityNoncurrentReclassification	12400000	usd
CY2024Q3	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	37800000	usd
CY2024Q3	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	9800000	usd
CY2024Q3	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	200000	usd
CY2024Q3	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	217000000.0	usd
CY2024Q3	us-gaap	Inventory Work In Process InventoryWorkInProcess	1188200000	usd
CY2024Q3	us-gaap	Inventory Finished Goods InventoryFinishedGoods	81000000.0	usd
CY2024Q3	us-gaap	Inventory Gross InventoryGross	1486200000	usd
CY2024Q3	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	71700000	usd
CY2024Q3	us-gaap	Inventory Net InventoryNet	1414500000	usd
CY2023Q4	us-gaap	Inventory Net InventoryNet	1247500000	usd
CY2024Q3	us-gaap	Land Land	30900000	usd
CY2023Q4	us-gaap	Land Land	32300000	usd
CY2024Q3	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	711200000	usd
CY2024Q3	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	3099200000	usd
CY2024Q3	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	3841300000	usd
CY2024Q3	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	2094800000	usd
CY2023Q4	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	75500000	usd
CY2024Q3	us-gaap	Inventory Net InventoryNet	1414500000	usd
CY2024Q3	us-gaap	Land Land	30900000	usd
CY2024Q3	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	711200000	usd
CY2023Q4	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	692700000	usd
CY2024Q3	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	3099200000	usd
CY2024Q3	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	3841300000	usd
CY2024Q3	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	2094800000	usd
CY2023Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	2083400000	usd
CY2024Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1746500000	usd
CY2024Q3	us-gaap	Construction In Progress Gross ConstructionInProgressGross	259800000	usd
	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	28300000	usd
CY2024Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1746500000	usd
CY2024Q3	us-gaap	Construction In Progress Gross ConstructionInProgressGross	259800000	usd
	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	28300000	usd
CY2024Q3	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	700000	usd
CY2023Q4	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	700000	usd
	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	2300000	usd
	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	2000000.0	usd
CY2024Q3	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	3700000	usd
	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	300000	usd
CY2024Q3	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-200000	usd
CY2023Q4	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-700000	usd
	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-1000000.0	usd
	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-1000000.0	usd
CY2024Q3	ati	Other Other Nonoperating Income Expense OtherOtherNonoperatingIncomeExpense	200000	usd
CY2023Q4	ati	Other Other Nonoperating Income Expense OtherOtherNonoperatingIncomeExpense	0	usd
	ati	Other Other Nonoperating Income Expense OtherOtherNonoperatingIncomeExpense	200000	usd
	ati	Other Other Nonoperating Income Expense OtherOtherNonoperatingIncomeExpense	0	usd
CY2024Q3	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	4400000	usd
	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	5200000	usd
	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	1300000	usd
CY2024Q3	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	3700000	usd
CY2024Q3	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	500000	usd
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-1200000	usd
	ati	Restructuring And Related Costs Number Of Positions With Decreased Severance Related Reserve RestructuringAndRelatedCostsNumberOfPositionsWithDecreasedSeveranceRelatedReserve	80	employee
CY2024Q3	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	700000	usd
CY2023Q4	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	700000	usd
	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	2300000	usd
	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	2000000.0	usd
CY2024Q3	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	3700000	usd
CY2023Q4	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	0	usd
	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	3700000	usd
	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	300000	usd
CY2024Q3	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-200000	usd
CY2023Q4	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-700000	usd
	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-1000000.0	usd
	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-1000000.0	usd
CY2024Q3	ati	Other Other Nonoperating Income Expense OtherOtherNonoperatingIncomeExpense	200000	usd
CY2023Q4	ati	Other Other Nonoperating Income Expense OtherOtherNonoperatingIncomeExpense	0	usd
	ati	Other Other Nonoperating Income Expense OtherOtherNonoperatingIncomeExpense	200000	usd
	ati	Other Other Nonoperating Income Expense OtherOtherNonoperatingIncomeExpense	0	usd
CY2024Q3	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	4400000	usd
CY2023Q4	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	0	usd
	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	5200000	usd
	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	1300000	usd
CY2024Q3	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	3700000	usd
CY2024Q3	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	500000	usd
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-1200000	usd
	ati	Restructuring And Related Costs Number Of Positions With Decreased Severance Related Reserve RestructuringAndRelatedCostsNumberOfPositionsWithDecreasedSeveranceRelatedReserve	80	employee
CY2023Q4	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-500000	usd
CY2023Q4	ati	Restructuring And Related Costs Number Of Positions With Decreased Severance Related Reserve RestructuringAndRelatedCostsNumberOfPositionsWithDecreasedSeveranceRelatedReserve	10	employee
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	2200000	usd
	us-gaap	Restructuring And Related Cost Number Of Positions Eliminated RestructuringAndRelatedCostNumberOfPositionsEliminated	40	employee
CY2023Q4	us-gaap	Restructuring Reserve RestructuringReserve	15200000	usd
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-1200000	usd
	us-gaap	Payments For Restructuring PaymentsForRestructuring	5200000	usd
CY2024Q3	us-gaap	Restructuring Reserve RestructuringReserve	8800000	usd
CY2024Q3	us-gaap	Restructuring Reserve RestructuringReserve	8800000	usd
CY2024Q3	us-gaap	Supplier Finance Program Obligation Current SupplierFinanceProgramObligationCurrent	58400000	usd
CY2023Q4	us-gaap	Supplier Finance Program Obligation Current SupplierFinanceProgramObligationCurrent	15600000	usd
CY2023Q4	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-500000	usd
CY2023Q4	ati	Restructuring And Related Costs Number Of Positions With Decreased Severance Related Reserve RestructuringAndRelatedCostsNumberOfPositionsWithDecreasedSeveranceRelatedReserve	10	employee
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	2200000	usd
	us-gaap	Restructuring And Related Cost Number Of Positions Eliminated RestructuringAndRelatedCostNumberOfPositionsEliminated	40	employee
CY2023Q4	us-gaap	Restructuring Reserve RestructuringReserve	15200000	usd
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-1200000	usd
	us-gaap	Payments For Restructuring PaymentsForRestructuring	5200000	usd
CY2024Q3	us-gaap	Restructuring Reserve RestructuringReserve	8800000	usd
CY2024Q3	us-gaap	Restructuring Reserve RestructuringReserve	8800000	usd
CY2024Q3	us-gaap	Supplier Finance Program Obligation Current SupplierFinanceProgramObligationCurrent	58400000	usd
CY2023Q4	us-gaap	Supplier Finance Program Obligation Current SupplierFinanceProgramObligationCurrent	15600000	usd
CY2024Q3	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	14800000	usd
CY2023Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	19600000	usd
CY2024Q3	ati	Total Debt TotalDebt	1883400000	usd
CY2023Q4	ati	Total Debt TotalDebt	2179600000	usd
CY2024Q3	us-gaap	Debt Current DebtCurrent	27900000	usd
CY2023Q4	us-gaap	Debt Current DebtCurrent	31900000	usd
CY2024Q3	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	1855500000	usd
CY2023Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	2147700000	usd
CY2024Q3	us-gaap	Stock Issued During Period Value Conversion Of Convertible Securities StockIssuedDuringPeriodValueConversionOfConvertibleSecurities	291000000.0	usd
CY2024Q3	us-gaap	Stock Issued During Period Shares Conversion Of Convertible Securities StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities	18800000	shares
CY2024Q3	ati	Receipt Of Convertible Note Capped Call ReceiptOfConvertibleNoteCappedCall	76100000	usd
	ati	Percentage Of Raw Material Usage Hedged PercentageOfRawMaterialUsageHedged	0.06
	ati	Percentage Of Forecasted Natural Gas Usage Hedgedfor Year1 PercentageOfForecastedNaturalGasUsageHedgedforYear1	0.85
	ati	Percentage Of Forecasted Natural Gas Usage Hedgedfor Year2 PercentageOfForecastedNaturalGasUsageHedgedforYear2	0.55
	ati	Percentage Of Forecasted Natural Gas Usage Hedged For Year3 PercentageOfForecastedNaturalGasUsageHedgedForYear3	0.10
CY2024Q3	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	14800000	usd
CY2023Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	19600000	usd
CY2024Q3	ati	Total Debt TotalDebt	1883400000	usd
CY2023Q4	ati	Total Debt TotalDebt	2179600000	usd
CY2024Q3	us-gaap	Debt Current DebtCurrent	27900000	usd
CY2023Q4	us-gaap	Debt Current DebtCurrent	31900000	usd
CY2024Q3	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	1855500000	usd
CY2023Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	2147700000	usd
CY2024Q3	us-gaap	Stock Issued During Period Value Conversion Of Convertible Securities StockIssuedDuringPeriodValueConversionOfConvertibleSecurities	291000000.0	usd
CY2024Q3	us-gaap	Stock Issued During Period Shares Conversion Of Convertible Securities StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities	18800000	shares
CY2024Q3	ati	Receipt Of Convertible Note Capped Call ReceiptOfConvertibleNoteCappedCall	76100000	usd
	ati	Percentage Of Raw Material Usage Hedged PercentageOfRawMaterialUsageHedged	0.06
	ati	Percentage Of Forecasted Natural Gas Usage Hedgedfor Year1 PercentageOfForecastedNaturalGasUsageHedgedforYear1	0.85
	ati	Percentage Of Forecasted Natural Gas Usage Hedgedfor Year2 PercentageOfForecastedNaturalGasUsageHedgedforYear2	0.55
	ati	Percentage Of Forecasted Natural Gas Usage Hedged For Year3 PercentageOfForecastedNaturalGasUsageHedgedForYear3	0.10
	us-gaap	Cash Flow Hedge Gain Loss To Be Reclassified Within Twelve Months CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths	-5100000	usd
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2024Q3	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	196800000	usd
CY2023Q4	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	178700000	usd
	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	567500000	usd
	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	527800000	usd
CY2024Q3	ati	Corporate Expenses CorporateExpenses	13400000	usd
CY2023Q4	ati	Corporate Expenses CorporateExpenses	12500000	usd
	ati	Corporate Expenses CorporateExpenses	49900000	usd
	ati	Corporate Expenses CorporateExpenses	47100000	usd
CY2024Q3	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	2300000	usd
CY2023Q4	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	-3600000	usd
	us-gaap	Cash Flow Hedge Gain Loss To Be Reclassified Within Twelve Months CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths	-5100000	usd
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2024Q3	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	196800000	usd
CY2023Q4	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	178700000	usd
	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	567500000	usd
	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	527800000	usd
CY2024Q3	ati	Corporate Expenses CorporateExpenses	13400000	usd
CY2023Q4	ati	Corporate Expenses CorporateExpenses	12500000	usd
	ati	Corporate Expenses CorporateExpenses	49900000	usd
	ati	Corporate Expenses CorporateExpenses	47100000	usd
CY2024Q3	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	2300000	usd
CY2023Q4	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	-3600000	usd
	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	1700000	usd
	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	-6800000	usd
CY2024Q3	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	38500000	usd
CY2023Q4	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	35600000	usd
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	112400000	usd
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	106600000	usd
CY2024Q3	ati	Interest Expense Net InterestExpenseNet	28000000.0	usd
CY2023Q4	ati	Interest Expense Net InterestExpenseNet	23800000	usd
	ati	Interest Expense Net InterestExpenseNet	83000000.0	usd
	ati	Interest Expense Net InterestExpenseNet	65000000.0	usd
CY2024Q3	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	4300000	usd
CY2023Q4	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	4200000	usd
	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	12800000	usd
	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	14600000	usd
CY2024Q3	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	0	usd
CY2023Q4	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	0	usd
CY2024Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	114900000	usd
CY2023Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	99000000.0	usd
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	287100000	usd
CY2024Q3	ati	Employee Retention Credits EmployeeRetentionCredits	4800000	usd
CY2024Q3	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	4300000	usd
CY2024Q3	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	500000	usd
	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	12800000	usd
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-1200000	usd
CY2023Q4	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	4200000	usd
CY2023Q4	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-500000	usd
	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	14600000	usd
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	2200000	usd
CY2024Q3	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.246
	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	1700000	usd
	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	-6800000	usd
CY2024Q3	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	38500000	usd
CY2023Q4	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	35600000	usd
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	112400000	usd
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	106600000	usd
CY2024Q3	ati	Interest Expense Net InterestExpenseNet	28000000.0	usd
CY2023Q4	ati	Interest Expense Net InterestExpenseNet	23800000	usd
	ati	Interest Expense Net InterestExpenseNet	83000000.0	usd
	ati	Interest Expense Net InterestExpenseNet	65000000.0	usd
CY2024Q3	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	4300000	usd
CY2023Q4	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	4200000	usd
	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	12800000	usd
	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	14600000	usd
CY2024Q3	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	0	usd
CY2023Q4	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	0	usd
	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	0	usd
CY2024Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	114900000	usd
CY2023Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	99000000.0	usd
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	311100000	usd
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	287100000	usd
CY2024Q3	ati	Employee Retention Credits EmployeeRetentionCredits	4800000	usd
	ati	Employee Retention Credits EmployeeRetentionCredits	13400000	usd
CY2024Q3	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	3700000	usd
CY2024Q3	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	4300000	usd
CY2024Q3	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	500000	usd
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-1200000	usd
CY2023Q4	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	4200000	usd
CY2023Q4	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-500000	usd
	ati	Restructuring And Other Credits Charges RestructuringAndOtherCreditsCharges	14600000	usd
	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	2200000	usd
CY2024Q3	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.246
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.227
CY2024Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	28300000	usd
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	70500000	usd
	us-gaap	Income Tax Reconciliation Other Reconciling Items IncomeTaxReconciliationOtherReconcilingItems	-4500000	usd
	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	3300000	usd
CY2023Q4	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.049
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.045
CY2024Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	82700000	usd
CY2024Q3	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	84400000	usd
CY2023Q4	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	92900000	usd
CY2024Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	128700000	shares
CY2023Q4	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	128100000	shares
CY2024Q3	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	3700000	shares
CY2023Q4	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	3300000	shares
CY2024Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	146800000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	146900000	shares
CY2024Q3	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.64
CY2023Q4	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.70
	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	1.82
CY2024Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.57
CY2023Q4	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.62
	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.61
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2024Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2024Q3	srt	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	700000000	usd
CY2024Q3	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	40000000.0	usd
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	190000000.0	usd
CY2024Q3	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	700000	shares
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	4100000	shares
CY2024Q3	ati	Share Repurchase Program Utilized Amount ShareRepurchaseProgramUtilizedAmount	40000000	usd
CY2024Q3	srt	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	700000000	usd
CY2023Q4	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	1000000	shares
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	55100000	usd
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	1200000	shares
CY2024Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-90200000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	11900000	usd
CY2024Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-3700000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	15600000	usd
CY2024Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-74600000	usd
CY2024Q2	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	6500000	usd
CY2024Q3	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	4000000.0	usd
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.227
CY2024Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	28300000	usd
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	70500000	usd
	us-gaap	Income Tax Reconciliation Other Reconciling Items IncomeTaxReconciliationOtherReconcilingItems	-4500000	usd
	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	3300000	usd
CY2023Q4	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.049
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.045
CY2024Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	82700000	usd
	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	265100000	usd
CY2024Q3	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	84400000	usd
CY2023Q4	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	92900000	usd
	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	236700000	usd
	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	273000000.0	usd
CY2024Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	128700000	shares
CY2023Q4	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	128100000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	126500000	shares
CY2024Q3	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	3700000	shares
CY2023Q4	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	3300000	shares
CY2024Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	146800000	shares
CY2023Q4	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	150200000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	146900000	shares
CY2024Q3	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.64
CY2023Q4	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.70
	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	1.82
CY2024Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.57
CY2023Q4	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.62
	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.61
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2024Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2024Q3	srt	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	700000000	usd
CY2024Q3	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	40000000.0	usd
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	190000000.0	usd
CY2024Q3	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	700000	shares
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	4100000	shares
CY2024Q3	ati	Share Repurchase Program Utilized Amount ShareRepurchaseProgramUtilizedAmount	40000000	usd
CY2024Q3	srt	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	700000000	usd
CY2023Q4	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	45000000.0	usd
CY2023Q4	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	1000000	shares
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	55100000	usd
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	1200000	shares
CY2024Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-90200000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	11900000	usd
CY2024Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-3700000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	15600000	usd
CY2024Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-74600000	usd
CY2024Q2	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	6500000	usd
CY2024Q3	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	4000000.0	usd
CY2024Q3	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	usd
CY2024Q3	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	4000000.0	usd
CY2024Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	10500000	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-83200000	usd
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	600000	usd
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-8000000.0	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	8600000	usd
CY2024Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-74600000	usd
CY2023Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	7300000	usd
	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	3200000	usd
	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	3200000	usd
CY2023Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-87300000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-9500000	usd
CY2023Q4	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-2400000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-7100000	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-94400000	usd
CY2023Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	6400000	usd
CY2023Q4	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	-2100000	usd
CY2023Q4	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	-2100000	usd
CY2023Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	4300000	usd
CY2023Q1	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-67400000	usd
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-26300000	usd
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	700000	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-27000000.0	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-94400000	usd
CY2023Q1	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	7700000	usd
	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	-3400000	usd
	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	usd
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CY2023Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	4300000	usd
CY2024Q3	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	12000000	usd
CY2024Q3	us-gaap	Accrued Environmental Loss Contingencies Current AccruedEnvironmentalLossContingenciesCurrent	6000000	usd
CY2024Q3	ati	Environmental Remediation Obligation Federal Superfund Sites EnvironmentalRemediationObligationFederalSuperfundSites	3000000	usd
CY2024Q3	ati	Environmental Remediation Obligation For Formerly Owned Sites EnvironmentalRemediationObligationForFormerlyOwnedSites	7000000	usd
CY2024Q3	ati	Environmental Remediation Obligation For Owned Or Controlled Sites With Closed Operations EnvironmentalRemediationObligationForOwnedOrControlledSitesWithClosedOperations	2000000	usd
CY2024Q3	ati	Employee Retention Credits EmployeeRetentionCredits	4800000	usd
	ati	Employee Retention Credits EmployeeRetentionCredits	13400000	usd
CY2024Q3	ecd	Rule10b51 Arr Adopted Flag Rule10b51ArrAdoptedFlag	false
CY2024Q3	ecd	Non Rule10b51 Arr Adopted Flag NonRule10b51ArrAdoptedFlag	false
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CY2024Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	4000000.0	usd
CY2024Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	10500000	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-83200000	usd
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	600000	usd
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-8000000.0	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	8600000	usd
CY2023Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	7300000	usd
	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	3200000	usd
	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	3200000	usd
CY2024Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	10500000	usd
CY2023Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-87300000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-9500000	usd
CY2023Q4	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-2400000	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-7100000	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-94400000	usd
CY2023Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	6400000	usd
CY2023Q4	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	-2100000	usd
CY2023Q4	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	usd
CY2023Q4	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	-2100000	usd
CY2023Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	4300000	usd
CY2023Q1	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-67400000	usd
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-26300000	usd
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	700000	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-27000000.0	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-94400000	usd
CY2023Q1	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	7700000	usd
	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	-3400000	usd
	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	-3400000	usd
CY2023Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	4300000	usd
CY2024Q3	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	12000000	usd
CY2024Q3	us-gaap	Accrued Environmental Loss Contingencies Current AccruedEnvironmentalLossContingenciesCurrent	6000000	usd
CY2024Q3	ati	Environmental Remediation Obligation Federal Superfund Sites EnvironmentalRemediationObligationFederalSuperfundSites	3000000	usd
CY2024Q3	ati	Environmental Remediation Obligation For Formerly Owned Sites EnvironmentalRemediationObligationForFormerlyOwnedSites	7000000	usd
CY2024Q3	ati	Environmental Remediation Obligation For Owned Or Controlled Sites With Closed Operations EnvironmentalRemediationObligationForOwnedOrControlledSitesWithClosedOperations	2000000	usd
CY2024Q3	ati	Employee Retention Credits EmployeeRetentionCredits	4800000	usd
	ati	Employee Retention Credits EmployeeRetentionCredits	13400000	usd
CY2024Q3	ecd	Rule10b51 Arr Adopted Flag Rule10b51ArrAdoptedFlag	false
CY2024Q3	ecd	Non Rule10b51 Arr Adopted Flag NonRule10b51ArrAdoptedFlag	false
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CY2024Q3	ecd	Non Rule10b51 Arr Trmntd Flag NonRule10b51ArrTrmntdFlag	false

Files In Submission

Name	View Source	Status
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0001628280-24-044066-index.html	Edgar Link	pending
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R7.htm	Edgar Link	pending
R8.htm	Edgar Link	pending
R9.htm	Edgar Link	pending
report.css	Edgar Link	pending
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ati-20240929_cal.xml	Edgar Link	unprocessable
ati-20240929_def.xml	Edgar Link	unprocessable

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$ATI
ATI INC Stock $ati

2024 Q4 Form 10-Q Financial Statement

#000162828024044066 Filed on October 29, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ATI ATI INC Stock $ati

2024 Q4 Form 10-Q Financial Statement

#000162828024044066 Filed on October 29, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ATI
ATI INC Stock $ati