$ATI
ATI INC Stock $ati

$ati Overview Financials Valuation SEC Filings Company Website

2021 Q4 Form 10-K Financial Statement

#000162828022003961 Filed on February 25, 2022

Income Statement

Concept	2021 Q4	2021	2020 Q4
Revenue	$765.4M	$2.800B	$658.3M
YoY Change	16.27%	-6.11%	-35.37%
Cost Of Revenue	$643.2M	$2.467B	$613.1M
YoY Change	4.91%	-8.28%	-27.81%
Gross Profit	$122.2M	$333.2M	$45.20M
YoY Change	170.35%	13.8%	-73.3%
Gross Profit Margin	15.97%	11.9%	6.87%
Selling, General & Admin	$57.80M	$226.9M	$52.80M
YoY Change	9.47%	12.89%	-20.36%
% of Gross Profit	47.3%	68.1%	116.81%
Research & Development		$16.50M
YoY Change		17.02%
% of Gross Profit		4.95%
Depreciation & Amortization	$35.90M	$143.9M	$35.00M
YoY Change	2.57%	0.42%	-4.11%
% of Gross Profit	29.38%	43.19%	77.43%
Operating Expenses	$57.80M	$243.4M	$52.80M
YoY Change	9.47%	13.16%	-20.36%
Operating Profit	$64.40M	$117.6M	-$7.600M
YoY Change	-947.37%	-109.03%	-107.38%
Interest Expense	-$25.00M	-$96.80M	-$26.10M
YoY Change	-4.21%	-4.54%	0.0%
% of Operating Profit	-38.82%	-82.31%
Other Income/Expense, Net	-$6.500M	$18.20M	-$28.20M
YoY Change	-76.95%	-1616.67%	54.1%
Pretax Income	-$29.30M	$10.60M	-$1.143B
YoY Change	-97.44%	-100.72%	-5490.57%
Income Tax	-$4.700M	$26.80M	-$26.50M
% Of Pretax Income		252.83%
Net Earnings	-$29.80M	-$38.20M	-$1.121B
YoY Change	-97.34%	-97.57%	-2084.07%
Net Earnings / Revenue	-3.89%	-1.36%	-170.29%
Basic Earnings Per Share		-$0.30	-$8.85
Diluted Earnings Per Share	-$233.9K	-$0.30	-$8.85
COMMON SHARES
Basic Shares Outstanding	127.2M shares	127.1M shares	126.8M shares
Diluted Shares Outstanding		127.1M shares

Balance Sheet

Concept	2021 Q4	2021	2020 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments	$687.7M	$687.7M	$645.9M
YoY Change	6.47%	6.47%	31.6%
Cash & Equivalents	$687.7M		$645.9M
Short-Term Investments		$464.9M
Other Short-Term Assets	$48.80M	$48.80M	$38.30M
YoY Change	27.42%	27.42%	-40.44%
Inventory	$1.046B	$1.046B	$997.1M
Prepaid Expenses
Receivables	$470.0M	$523.9M	$345.8M
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$2.307B	$2.307B	$2.066B
YoY Change	11.65%	11.65%	-10.29%
LONG-TERM ASSETS
Property, Plant & Equipment	$1.529B	$1.529B	$1.469B
YoY Change	4.04%	4.04%	-40.04%
Goodwill	$227.9M		$240.7M
YoY Change	-5.32%		-54.22%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets	$222.1M	$156.2M	$259.0M
YoY Change	-14.25%	-8.71%	-27.19%
Total Long-Term Assets	$1.979B	$1.979B	$1.969B
YoY Change	0.49%	0.49%	-40.9%
TOTAL ASSETS
Total Short-Term Assets	$2.307B	$2.307B	$2.066B
Total Long-Term Assets	$1.979B	$1.979B	$1.969B
Total Assets	$4.285B	$4.285B	$4.035B
YoY Change	6.2%	6.2%	-28.39%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$375.5M	$375.5M	$290.6M
YoY Change	29.22%	29.22%	-44.24%
Accrued Expenses	$233.4M	$107.9M	$233.1M
YoY Change	0.13%	-2.62%	-1.98%
Deferred Revenue	$116.2M		$111.8M
YoY Change	3.94%		42.06%
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due	$131.3M	$131.3M	$17.80M
YoY Change	637.64%	637.64%	54.78%
Total Short-Term Liabilities	$856.4M	$856.4M	$653.3M
YoY Change	31.09%	31.09%	-23.07%
LONG-TERM LIABILITIES
Long-Term Debt	$1.712B	$1.712B	$1.550B
YoY Change	10.43%	10.43%	11.72%
Other Long-Term Liabilities	$211.0M	$884.5M	$189.9M
YoY Change	11.11%	-25.68%	18.1%
Total Long-Term Liabilities	$211.0M	$2.596B	$189.9M
YoY Change	11.11%	-5.26%	18.1%
TOTAL LIABILITIES
Total Short-Term Liabilities	$856.4M	$856.4M	$653.3M
Total Long-Term Liabilities	$211.0M	$2.596B	$189.9M
Total Liabilities	$3.453B	$3.600B	$3.394B
YoY Change	1.74%	2.44%	-1.39%
SHAREHOLDERS EQUITY
Retained Earnings	$72.70M		$106.5M
YoY Change	-31.74%		-93.66%
Common Stock	$1.609B		$1.638B
YoY Change	-1.76%		0.46%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$4.800M		$0.00
YoY Change			-100.0%
Treasury Stock Shares	231.9K shares		2.672K shares
Shareholders Equity	$685.6M	$685.6M	$521.1M
YoY Change
Total Liabilities & Shareholders Equity	$4.285B	$4.285B	$4.035B
YoY Change	6.2%	6.2%	-28.39%

Cashflow Statement

Concept	2021 Q4	2021	2020 Q4
OPERATING ACTIVITIES
Net Income	-$29.80M	-$38.20M	-$1.121B
YoY Change	-97.34%	-97.57%	-2084.07%
Depreciation, Depletion And Amortization	$35.90M	$143.9M	$35.00M
YoY Change	2.57%	0.42%	-4.11%
Cash From Operating Activities	$260.9M	$16.10M	$121.9M
YoY Change	114.03%	-90.35%	-49.23%
INVESTING ACTIVITIES
Capital Expenditures	-$48.40M	-$152.6M	-$41.90M
YoY Change	15.51%	11.79%	-40.23%
Acquisitions
YoY Change
Other Investing Activities	$19.60M	-$1.400M	$2.400M
YoY Change	716.67%	-26.32%	0.0%
Cash From Investing Activities	-$28.80M	-$77.30M	-$39.50M
YoY Change	-27.09%	-39.94%	-41.65%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-551.2M	$103.0M	-8.700M
YoY Change	6235.63%	-11.89%	-95.49%
NET CHANGE
Cash From Operating Activities	260.9M	$16.10M	121.9M
Cash From Investing Activities	-28.80M	-$77.30M	-39.50M
Cash From Financing Activities	-551.2M	$103.0M	-8.700M
Net Change In Cash	-319.1M	$41.80M	73.70M
YoY Change	-532.97%	-73.05%	-459.51%
FREE CASH FLOW
Cash From Operating Activities	$260.9M	$16.10M	$121.9M
Capital Expenditures	-$48.40M	-$152.6M	-$41.90M
Free Cash Flow	$309.3M	$168.7M	$163.8M
YoY Change	88.83%	-44.4%	-47.2%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2021	dei	Amendment Flag AmendmentFlag	false
CY2021	dei	Entity Central Index Key EntityCentralIndexKey	0001018963
CY2021	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2021
CY2021	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2021	us-gaap	Accounting Standards Update Extensible List AccountingStandardsUpdateExtensibleList	http://fasb.org/us-gaap/2021-01-31#AccountingStandardsUpdate202006Member
CY2021Q4	us-gaap	Operating Lease Right Of Use Asset Statement Of Financial Position Extensible List OperatingLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherAssetsNoncurrent
CY2021Q4	us-gaap	Finance Lease Right Of Use Asset Statement Of Financial Position Extensible List FinanceLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#PropertyPlantAndEquipmentNet
CY2021Q4	us-gaap	Operating Lease Liability Current Statement Of Financial Position Extensible List OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherLiabilitiesCurrent
CY2021Q4	us-gaap	Operating Lease Liability Noncurrent Statement Of Financial Position Extensible List OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#OtherLiabilitiesNoncurrent
CY2021Q4	us-gaap	Finance Lease Liability Current Statement Of Financial Position Extensible List FinanceLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#DebtCurrent
CY2021Q4	us-gaap	Finance Lease Liability Noncurrent Statement Of Financial Position Extensible List FinanceLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#LongTermDebtAndCapitalLeaseObligations
CY2021Q4	us-gaap	Finance Lease Liability Statement Of Financial Position Extensible List FinanceLeaseLiabilityStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2021-01-31#Liabilities
CY2021	dei	Document Type DocumentType	10-K
CY2021	dei	Document Annual Report DocumentAnnualReport	true
CY2021	dei	Document Period End Date DocumentPeriodEndDate	2021-12-31
CY2021	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2021	dei	Document Transition Report DocumentTransitionReport	false
CY2021	dei	Entity File Number EntityFileNumber	1-12001
CY2021	dei	Entity Registrant Name EntityRegistrantName	ALLEGHENY TECHNOLOGIES INCORPORATED
CY2021	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
CY2021	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	25-1792394
CY2021	dei	Entity Address Address Line1 EntityAddressAddressLine1	1000 Six PPG Place
CY2021	dei	Entity Address City Or Town EntityAddressCityOrTown	Pittsburgh,
CY2021	dei	Entity Address State Or Province EntityAddressStateOrProvince	PA
CY2021	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	15222-5479
CY2021	dei	City Area Code CityAreaCode	412
CY2021	dei	Local Phone Number LocalPhoneNumber	394-2800
CY2021	dei	Security12b Title Security12bTitle	Common stock, par value $0.10
CY2021	dei	Trading Symbol TradingSymbol	ATI
CY2021	dei	Security Exchange Name SecurityExchangeName	NYSE
CY2021	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2021	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2021	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2021	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2021	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2021	dei	Entity Small Business EntitySmallBusiness	false
CY2021	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2021	dei	Icfr Auditor Attestation Flag IcfrAuditorAttestationFlag	true
CY2021	dei	Entity Shell Company EntityShellCompany	false
CY2022Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	127447661	shares
CY2021Q2	dei	Entity Public Float EntityPublicFloat	2700000000	USD
CY2021	us-gaap	Operating Income Loss OperatingIncomeLoss	117600000	USD
CY2020	us-gaap	Operating Income Loss OperatingIncomeLoss	-1302700000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	366300000	USD
CY2021	dei	Auditor Name AuditorName	Ernst & Young LLP
CY2021	dei	Auditor Location AuditorLocation	Pittsburgh, Pennsylvania
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CY2021	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	2466600000	USD
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CY2020	us-gaap	Gross Profit GrossProfit	292800000	USD
CY2019	us-gaap	Gross Profit GrossProfit	638000000.0	USD
CY2021	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	226900000	USD
CY2020	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	201000000.0	USD
CY2019	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	267200000	USD
CY2021	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000.0	USD
CY2019	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2021	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	-11300000	USD
CY2020	ati	Restructuring Settlement And Impairment Provisions Excluding Goodwill Impairment Loss RestructuringSettlementAndImpairmentProvisionsExcludingGoodwillImpairmentLoss	1107500000	USD
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CY2021	ati	Nonoperatingretirementbenefitexpense Nonoperatingretirementbenefitexpense	-37200000	USD
CY2020	ati	Nonoperatingretirementbenefitexpense Nonoperatingretirementbenefitexpense	62100000	USD
CY2019	ati	Nonoperatingretirementbenefitexpense Nonoperatingretirementbenefitexpense	73600000	USD
CY2021	ati	Interest Expense Net InterestExpenseNet	96900000	USD
CY2020	ati	Interest Expense Net InterestExpenseNet	94400000	USD
CY2019	ati	Interest Expense Net InterestExpenseNet	99000000.0	USD
CY2021	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-65500000	USD
CY2020	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21500000	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21600000	USD
CY2021	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	18200000	USD
CY2020	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-1200000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	64400000	USD
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	10600000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-1481900000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	236500000	USD
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26800000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	77700000	USD
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CY2021	us-gaap	Profit Loss ProfitLoss	-16200000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	-1559600000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	265000000.0	USD
CY2021	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	22000000.0	USD
CY2020	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	13000000.0	USD
CY2019	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	12500000	USD
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CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.30
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CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	9700000	USD
CY2021	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	11400000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	-6000000.0	USD
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CY2021	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-89500000	USD
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CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-87200000	USD
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CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-180500000	USD
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CY2020	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	-3100000	USD
CY2019	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	-2600000	USD
CY2021	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	-21900000	USD
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CY2019	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	0	USD
CY2021	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	15500000	USD
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CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	20400000	USD
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CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	46200000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	75500000	USD
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	236700000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-10500000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-69200000	USD
CY2021	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	220500000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	-1570100000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	195800000	USD
CY2021	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	26800000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	24400000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	11200000	USD
CY2021	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	193700000	USD
CY2021Q4	us-gaap	Goodwill Goodwill	227900000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-1594500000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	184600000	USD
CY2021Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	687700000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	645900000	USD
CY2021Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	470000000.0	USD
CY2020Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	345800000	USD
CY2021Q4	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	53900000	USD
CY2020Q4	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	38900000	USD
CY2021Q4	us-gaap	Inventory Net InventoryNet	1046300000	USD
CY2020Q4	us-gaap	Inventory Net InventoryNet	997100000	USD
CY2021Q4	us-gaap	Other Assets Current OtherAssetsCurrent	48800000	USD
CY2020Q4	us-gaap	Other Assets Current OtherAssetsCurrent	38300000	USD
CY2021Q4	us-gaap	Assets Current AssetsCurrent	2306700000	USD
CY2020Q4	us-gaap	Assets Current AssetsCurrent	2066000000	USD
CY2021Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1528500000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1469200000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	240700000	USD
CY2021Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	222100000	USD
CY2020Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	259000000.0	USD
CY2021Q4	us-gaap	Assets Assets	4285200000	USD
CY2020Q4	us-gaap	Assets Assets	4034900000	USD
CY2021Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	375500000	USD
CY2020Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	290600000	USD
CY2021Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	116200000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	111800000	USD
CY2021Q4	us-gaap	Debt Current DebtCurrent	131300000	USD
CY2020Q4	us-gaap	Debt Current DebtCurrent	17800000	USD
CY2021Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	233400000	USD
CY2020Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	233100000	USD
CY2021Q4	us-gaap	Liabilities Current LiabilitiesCurrent	856400000	USD
CY2020Q4	us-gaap	Liabilities Current LiabilitiesCurrent	653300000	USD
CY2021Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	1711600000	USD
CY2020Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	1550000000	USD
CY2021Q4	us-gaap	Other Postretirement Defined Benefit Plan Liabilities Noncurrent OtherPostretirementDefinedBenefitPlanLiabilitiesNoncurrent	258100000	USD
CY2020Q4	us-gaap	Other Postretirement Defined Benefit Plan Liabilities Noncurrent OtherPostretirementDefinedBenefitPlanLiabilitiesNoncurrent	326700000	USD
CY2021Q4	us-gaap	Defined Benefit Pension Plan Liabilities Noncurrent DefinedBenefitPensionPlanLiabilitiesNoncurrent	415400000	USD
CY2020Q4	us-gaap	Defined Benefit Pension Plan Liabilities Noncurrent DefinedBenefitPensionPlanLiabilitiesNoncurrent	673600000	USD
CY2021Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	211000000.0	USD
CY2020Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	189900000	USD
CY2021Q4	us-gaap	Liabilities Liabilities	3452500000	USD
CY2020Q4	us-gaap	Liabilities Liabilities	3393500000	USD
CY2021Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.10
CY2020Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.10
CY2020Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	50000000	shares
CY2021Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	50000000	shares
CY2021Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2020Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2021Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2020Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2021Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.10
CY2020Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.10
CY2021Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	500000000	shares
CY2020Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	500000000	shares
CY2021Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	127484902	shares
CY2020Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	126820440	shares
CY2021Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	127253045	shares
CY2020Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	126817768	shares
CY2021Q4	us-gaap	Common Stock Value CommonStockValue	12700000	USD
CY2020Q4	us-gaap	Common Stock Value CommonStockValue	12700000	USD
CY2021Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	1596700000	USD
CY2020Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	1625500000	USD
CY2021Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	72700000	USD
CY2020Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	106500000	USD
CY2021Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	231857	shares
CY2020Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	2672	shares
CY2021Q4	us-gaap	Treasury Stock Value TreasuryStockValue	4800000	USD
CY2020Q4	us-gaap	Treasury Stock Value TreasuryStockValue	0	USD
CY2021Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-991700000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1223600000	USD
CY2021Q4	us-gaap	Stockholders Equity StockholdersEquity	685600000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	521100000	USD
CY2021Q4	us-gaap	Minority Interest MinorityInterest	147100000	USD
CY2020Q4	us-gaap	Minority Interest MinorityInterest	120300000	USD
CY2021Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	832700000	USD
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	641400000	USD
CY2021Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	4285200000	USD
CY2020Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	4034900000	USD
CY2021	us-gaap	Profit Loss ProfitLoss	-16200000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	-1559600000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	265000000.0	USD
CY2021	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	143900000	USD
CY2020	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	143300000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	151100000	USD
CY2021	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	1000000.0	USD
CY2020	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	69900000	USD
CY2019	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-40900000	USD
CY2021	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000.0	USD
CY2019	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2021	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-65500000	USD
CY2020	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21500000	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21600000	USD
CY2021	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	2900000	USD
CY2020	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	2900000	USD
CY2019	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	90600000	USD
CY2021	us-gaap	Disposal Group Not Discontinued Operation Gain Loss On Disposal DisposalGroupNotDiscontinuedOperationGainLossOnDisposal	13800000	USD
CY2020	us-gaap	Disposal Group Not Discontinued Operation Gain Loss On Disposal DisposalGroupNotDiscontinuedOperationGainLossOnDisposal	0	USD
CY2019	us-gaap	Disposal Group Not Discontinued Operation Gain Loss On Disposal DisposalGroupNotDiscontinuedOperationGainLossOnDisposal	-7100000	USD
CY2021	us-gaap	Other Asset Impairment Charges OtherAssetImpairmentCharges	0	USD
CY2020	us-gaap	Other Asset Impairment Charges OtherAssetImpairmentCharges	1041500000	USD
CY2019	us-gaap	Other Asset Impairment Charges OtherAssetImpairmentCharges	0	USD
CY2021	ati	Non Cash Joint Venture Impairment Charge NonCashJointVentureImpairmentCharge	0	USD
CY2020	ati	Non Cash Joint Venture Impairment Charge NonCashJointVentureImpairmentCharge	0	USD
CY2019	ati	Non Cash Joint Venture Impairment Charge NonCashJointVentureImpairmentCharge	11400000	USD
CY2021	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	-110700000	USD
CY2020	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	-91900000	USD
CY2019	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	-103300000	USD
CY2021	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	126000000.0	USD
CY2020	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-208400000	USD
CY2019	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	52100000	USD
CY2021	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	53900000	USD
CY2020	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-158200000	USD
CY2019	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-25200000	USD
CY2021	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	88500000	USD
CY2020	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	-230500000	USD
CY2019	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	30100000	USD
CY2021	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	-2600000	USD
CY2020	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	2400000	USD
CY2019	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	4900000	USD
CY2021	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-43300000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-119600000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-600000	USD
CY2021	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	16100000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	166900000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	230100000	USD
CY2021	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	152600000	USD
CY2020	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	136500000	USD
CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	168200000	USD
CY2021	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	20800000	USD
CY2020	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	5900000	USD
CY2019	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	92000000.0	USD
CY2021	us-gaap	Proceeds From Divestiture Of Businesses And Interests In Affiliates ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates	53100000	USD
CY2020	us-gaap	Proceeds From Divestiture Of Businesses And Interests In Affiliates ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates	0	USD
CY2019	us-gaap	Proceeds From Divestiture Of Businesses And Interests In Affiliates ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates	158100000	USD
CY2021	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-1400000	USD
CY2020	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-1900000	USD
CY2019	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	200000	USD
CY2021	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-77300000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-128700000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	81700000	USD
CY2021	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	675700000	USD
CY2020	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	391400000	USD
CY2019	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	350000000.0	USD
CY2021	us-gaap	Repayments Of Long Term Debt And Capital Securities RepaymentsOfLongTermDebtAndCapitalSecurities	515600000	USD
CY2020	us-gaap	Repayments Of Long Term Debt And Capital Securities RepaymentsOfLongTermDebtAndCapitalSecurities	212100000	USD
CY2019	us-gaap	Repayments Of Long Term Debt And Capital Securities RepaymentsOfLongTermDebtAndCapitalSecurities	507600000	USD
CY2021	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	21700000	USD
CY2020	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	200000	USD
CY2019	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	4900000	USD
CY2021	ati	Payment Of Capped Call Transactions Cost PaymentOfCappedCallTransactionsCost	0	USD
CY2020	ati	Payment Of Capped Call Transactions Cost PaymentOfCappedCallTransactionsCost	19400000	USD
CY2019	ati	Payment Of Capped Call Transactions Cost PaymentOfCappedCallTransactionsCost	0	USD
CY2021	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	9500000	USD
CY2020	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	9100000	USD
CY2019	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	5500000	USD
CY2021	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	64500000	USD
CY2020	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	19100000	USD
CY2019	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	20900000	USD
CY2021	us-gaap	Payments Of Dividends Minority Interest PaymentsOfDividendsMinorityInterest	0	USD
CY2020	us-gaap	Payments Of Dividends Minority Interest PaymentsOfDividendsMinorityInterest	7200000	USD
CY2019	us-gaap	Payments Of Dividends Minority Interest PaymentsOfDividendsMinorityInterest	14000000.0	USD
CY2021	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	4800000	USD
CY2020	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	7800000	USD
CY2019	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	9900000	USD
CY2021	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	103000000.0	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	116900000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-203000000.0	USD
CY2021	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	41800000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	155100000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	108800000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	645900000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	490800000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	382000000.0	USD
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	687700000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	645900000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	490800000	USD
CY2018Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1991600000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	265000000.0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-69200000	USD
CY2019	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	14000000.0	USD
CY2019	ati	Employee Stock Plans EmployeeStockPlans	-14700000	USD
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	2193200000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	-1559600000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-10500000	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Equity Component Of Convertible Debt AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebt	49800000	USD
CY2020	ati	Adjustments To Additional Paid In Capital Convertible Note Capped Call AdjustmentsToAdditionalPaidInCapitalConvertibleNoteCappedCall	19400000	USD
CY2020	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	7200000	USD
CY2020	ati	Employee Stock Plans EmployeeStockPlans	4900000	USD
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	641400000	USD
CY2021	us-gaap	Profit Loss ProfitLoss	-16200000	USD
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	236700000	USD
CY2021	ati	Employee Stock Plans EmployeeStockPlans	-16200000	USD
CY2021Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	832700000	USD
CY2021	us-gaap	Use Of Estimates UseOfEstimates	<div style="margin-top:9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Risks and Uncertainties and Use of Estimates</span></div><div style="margin-top:9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The preparation of consolidated financial statements in conformity with United States generally accepted accounting principles requires management to make estimates and assumptions that affect reported amounts of assets and liabilities at the date of the financial statements, as well as the reported amounts of income and expenses during the reporting period. Actual results could differ from those estimates. Management believes that the estimates are reasonable. Certain prior year amounts have been reclassified in order to conform with the 2021 presentation.</span></div>
CY2021	us-gaap	Concentration Risk Credit Risk ConcentrationRiskCreditRisk	The Company markets its products to a diverse customer base, principally throughout the United States. No single customer accounted for more than 10% of sales for any year presented. The major end markets for the ATI’s products are customers in the aerospace & defense, energy, automotive, construction and mining, food equipment and appliances, and medical markets.
CY2021Q4	dei	Entity Number Of Employees EntityNumberOfEmployees	6300	employee
CY2021	ati	Employees Percent Non U.S. EmployeesPercentNonU.S.	0.20
CY2021	ati	Employees Percent Coveredby Collective Bargaining Agreements EmployeesPercentCoveredbyCollectiveBargainingAgreements	0.40
CY2021Q4	ati	Entity Number Of Employees Covered By Usw Collective Bargaining Agreements Expiring February282021 EntityNumberOfEmployeesCoveredByUSWCollectiveBargainingAgreementsExpiringFebruary282021	1100	employee
CY2021Q4	ati	Entity Number Of Employees Subject To Collective Bargaining Arrangements Expiring Within One Year EntityNumberOfEmployeesSubjectToCollectiveBargainingArrangementsExpiringWithinOneYear	800	employee
CY2021Q3	us-gaap	Percentage Of Lifo Inventory PercentageOfLIFOInventory	0.65
CY2021	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	2466600000	USD
CY2021Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	4285200000	USD
CY2021	us-gaap	Gross Profit GrossProfit	333200000	USD
CY2021	us-gaap	Operating Income Loss OperatingIncomeLoss	117600000	USD
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	10600000	USD
CY2021	us-gaap	Profit Loss ProfitLoss	-16200000	USD
CY2021	us-gaap	Net Income Loss NetIncomeLoss	-38200000	USD
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.30
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.30
CY2021	us-gaap	Profit Loss ProfitLoss	-16200000	USD
CY2021	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	220500000	USD
CY2021	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	193700000	USD
CY2021Q4	us-gaap	Inventory Net InventoryNet	1046300000	USD
CY2021Q4	us-gaap	Assets Current AssetsCurrent	2306700000	USD
CY2021Q4	us-gaap	Assets Assets	4285200000	USD
CY2021Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	72700000	USD
CY2021Q4	us-gaap	Stockholders Equity StockholdersEquity	685600000	USD
CY2021Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	832700000	USD
CY2021	us-gaap	Profit Loss ProfitLoss	-16200000	USD
CY2021	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	53900000	USD
CY2019	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	3484500000	USD
CY2019	us-gaap	Gross Profit GrossProfit	638000000.0	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	366300000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	64400000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	236500000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	265000000.0	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	252500000	USD
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.01
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.81
CY2019	us-gaap	Profit Loss ProfitLoss	265000000.0	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	195800000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	184600000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	265000000.0	USD
CY2019	us-gaap	Disposal Group Not Discontinued Operation Gain Loss On Disposal DisposalGroupNotDiscontinuedOperationGainLossOnDisposal	-7100000	USD
CY2019	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-25200000	USD
CY2018Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1427100000	USD
CY2021Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	3800000	USD
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	4300000	USD
CY2021	us-gaap	Research And Development Expense ResearchAndDevelopmentExpense	16500000	USD
CY2020	us-gaap	Research And Development Expense ResearchAndDevelopmentExpense	14100000	USD
CY2019	us-gaap	Research And Development Expense ResearchAndDevelopmentExpense	17800000	USD
CY2021	us-gaap	Research And Development Arrangement Contract To Perform For Others Costs Incurred Gross ResearchAndDevelopmentArrangementContractToPerformForOthersCostsIncurredGross	3500000	USD
CY2020	us-gaap	Research And Development Arrangement Contract To Perform For Others Costs Incurred Gross ResearchAndDevelopmentArrangementContractToPerformForOthersCostsIncurredGross	700000	USD
CY2019	us-gaap	Research And Development Arrangement Contract To Perform For Others Costs Incurred Gross ResearchAndDevelopmentArrangementContractToPerformForOthersCostsIncurredGross	2400000	USD
CY2021	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2021	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2021	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2799800000	USD
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2982100000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4122500000	USD
CY2021	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
CY2020	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4122500000	USD
CY2021	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2799800000	USD
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2982100000	USD
CY2019	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
CY2021Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	2100000000	USD
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	1400000000	USD
CY2019Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	2300000000	USD
CY2021Q4	ati	Revenue Remaining Performance Obligation Current RevenueRemainingPerformanceObligationCurrent	0.80	USD
CY2021Q4	ati	Accountsreceivablewithcustomers Accountsreceivablewithcustomers	473800000	USD
CY2020Q4	ati	Accountsreceivablewithcustomers Accountsreceivablewithcustomers	350100000	USD
CY2018Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	6000000.0	USD
CY2019	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	200000	USD
CY2019	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	1600000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	4600000	USD
CY2020	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	200000	USD
CY2020	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	500000	USD
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	4300000	USD
CY2021	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	300000	USD
CY2021	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	800000	USD
CY2021Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	3800000	USD
CY2020Q4	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	38900000	USD
CY2019Q4	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	38500000	USD
CY2018Q4	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	51200000	USD
CY2021	ati	Contractwith Customer Asset Current Period Increase ContractwithCustomerAssetCurrentPeriodIncrease	93800000	USD
CY2020	ati	Contractwith Customer Asset Current Period Increase ContractwithCustomerAssetCurrentPeriodIncrease	84200000	USD
CY2019	ati	Contractwith Customer Asset Current Period Increase ContractwithCustomerAssetCurrentPeriodIncrease	74500000	USD
CY2021	ati	Contractwith Customer Asset Current Reclassifiedto Receivable ContractwithCustomerAssetCurrentReclassifiedtoReceivable	76200000	USD
CY2020	ati	Contractwith Customer Asset Current Reclassifiedto Receivable ContractwithCustomerAssetCurrentReclassifiedtoReceivable	83900000	USD
CY2019	ati	Contractwith Customer Asset Current Reclassifiedto Receivable ContractwithCustomerAssetCurrentReclassifiedtoReceivable	79900000	USD
CY2021	ati	Contractwith Customer Asset Current Reclassification ContractwithCustomerAssetCurrentReclassification	2600000	USD
CY2020	ati	Contractwith Customer Asset Current Reclassification ContractwithCustomerAssetCurrentReclassification	-100000	USD
CY2019	ati	Contractwith Customer Asset Current Reclassification ContractwithCustomerAssetCurrentReclassification	0	USD
CY2021	ati	Contractwithcustomer Asset Current Divestiture ContractwithcustomerAssetCurrentDivestiture	0	USD
CY2020	ati	Contractwithcustomer Asset Current Divestiture ContractwithcustomerAssetCurrentDivestiture	0	USD
CY2019	ati	Contractwithcustomer Asset Current Divestiture ContractwithcustomerAssetCurrentDivestiture	7300000	USD
CY2021Q4	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	53900000	USD
CY2020Q4	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	38900000	USD
CY2019Q4	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	38500000	USD
CY2020Q4	us-gaap	Contract With Customer Asset Net Noncurrent ContractWithCustomerAssetNetNoncurrent	0	USD
CY2019Q4	us-gaap	Contract With Customer Asset Net Noncurrent ContractWithCustomerAssetNetNoncurrent	100000	USD
CY2018Q4	us-gaap	Contract With Customer Asset Net Noncurrent ContractWithCustomerAssetNetNoncurrent	100000	USD
CY2021	ati	Contractwith Customer Asset Nocurrent Period Increase ContractwithCustomerAssetNocurrentPeriodIncrease	0	USD
CY2020	ati	Contractwith Customer Asset Nocurrent Period Increase ContractwithCustomerAssetNocurrentPeriodIncrease	0	USD
CY2019	ati	Contractwith Customer Asset Nocurrent Period Increase ContractwithCustomerAssetNocurrentPeriodIncrease	0	USD
CY2021	ati	Contractwith Customer Asset Noncurrent Reclassifiedto Receivable ContractwithCustomerAssetNoncurrentReclassifiedtoReceivable	0	USD
CY2020	ati	Contractwith Customer Asset Noncurrent Reclassifiedto Receivable ContractwithCustomerAssetNoncurrentReclassifiedtoReceivable	0	USD
CY2019	ati	Contractwith Customer Asset Noncurrent Reclassifiedto Receivable ContractwithCustomerAssetNoncurrentReclassifiedtoReceivable	0	USD
CY2021	ati	Contractwith Customer Asset Noncurrent Reclassification ContractwithCustomerAssetNoncurrentReclassification	0	USD
CY2020	ati	Contractwith Customer Asset Noncurrent Reclassification ContractwithCustomerAssetNoncurrentReclassification	100000	USD
CY2019	ati	Contractwith Customer Asset Noncurrent Reclassification ContractwithCustomerAssetNoncurrentReclassification	0	USD
CY2021Q4	us-gaap	Contract With Customer Asset Net Noncurrent ContractWithCustomerAssetNetNoncurrent	0	USD
CY2020Q4	us-gaap	Contract With Customer Asset Net Noncurrent ContractWithCustomerAssetNetNoncurrent	0	USD
CY2019Q4	us-gaap	Contract With Customer Asset Net Noncurrent ContractWithCustomerAssetNetNoncurrent	100000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	111800000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	78700000	USD
CY2018Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	71400000	USD
CY2021	ati	Contractwith Customer Liability Current Period Increase ContractwithCustomerLiabilityCurrentPeriodIncrease	161500000	USD
CY2020	ati	Contractwith Customer Liability Current Period Increase ContractwithCustomerLiabilityCurrentPeriodIncrease	170300000	USD
CY2019	ati	Contractwith Customer Liability Current Period Increase ContractwithCustomerLiabilityCurrentPeriodIncrease	126100000	USD
CY2021	ati	Contractwith Customer Liability Current Reclassifiedto Revenue ContractwithCustomerLiabilityCurrentReclassifiedtoRevenue	-84100000	USD
CY2020	ati	Contractwith Customer Liability Current Reclassifiedto Revenue ContractwithCustomerLiabilityCurrentReclassifiedtoRevenue	-54900000	USD
CY2019	ati	Contractwith Customer Liability Current Reclassifiedto Revenue ContractwithCustomerLiabilityCurrentReclassifiedtoRevenue	-49200000	USD
CY2021	ati	Contractwith Customer Liability Current Revenue Recognized ContractwithCustomerLiabilityCurrentRevenueRecognized	-72900000	USD
CY2020	ati	Contractwith Customer Liability Current Revenue Recognized ContractwithCustomerLiabilityCurrentRevenueRecognized	-90100000	USD
CY2019	ati	Contractwith Customer Liability Current Revenue Recognized ContractwithCustomerLiabilityCurrentRevenueRecognized	-76000000.0	USD
CY2021	ati	Contract With Customers Liability Current Divestiture ContractWithCustomersLiabilityCurrentDivestiture	-800000	USD
CY2020	ati	Contract With Customers Liability Current Divestiture ContractWithCustomersLiabilityCurrentDivestiture	0	USD
CY2019	ati	Contract With Customers Liability Current Divestiture ContractWithCustomersLiabilityCurrentDivestiture	0	USD
CY2021	ati	Contractwith Customer Liability Current Other ContractwithCustomerLiabilityCurrentOther	100000	USD
CY2020	ati	Contractwith Customer Liability Current Other ContractwithCustomerLiabilityCurrentOther	0	USD
CY2019	ati	Contractwith Customer Liability Current Other ContractwithCustomerLiabilityCurrentOther	1900000	USD
CY2021	ati	Contractwith Customer Liability Current Reclassification ContractwithCustomerLiabilityCurrentReclassification	-600000	USD
CY2020	ati	Contractwith Customer Liability Current Reclassification ContractwithCustomerLiabilityCurrentReclassification	-7800000	USD
CY2019	ati	Contractwith Customer Liability Current Reclassification ContractwithCustomerLiabilityCurrentReclassification	-4500000	USD
CY2021Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	116200000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	111800000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	78700000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	32000000.0	USD
CY2019Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	25900000	USD
CY2018Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	7300000	USD
CY2021	ati	Contractwith Customer Liability Noncurrent Period Increase ContractwithCustomerLiabilityNoncurrentPeriodIncrease	56600000	USD
CY2020	ati	Contractwith Customer Liability Noncurrent Period Increase ContractwithCustomerLiabilityNoncurrentPeriodIncrease	14900000	USD
CY2019	ati	Contractwith Customer Liability Noncurrent Period Increase ContractwithCustomerLiabilityNoncurrentPeriodIncrease	24200000	USD
CY2021	ati	Contractwith Customer Liability Noncurrent Reclassifiedto Revenue ContractwithCustomerLiabilityNoncurrentReclassifiedtoRevenue	-1000000.0	USD
CY2020	ati	Contractwith Customer Liability Noncurrent Reclassifiedto Revenue ContractwithCustomerLiabilityNoncurrentReclassifiedtoRevenue	-1000000.0	USD
CY2019	ati	Contractwith Customer Liability Noncurrent Reclassifiedto Revenue ContractwithCustomerLiabilityNoncurrentReclassifiedtoRevenue	-1100000	USD
CY2021	ati	Contractwith Customer Liability Noncurrent Revenue Recognized ContractwithCustomerLiabilityNoncurrentRevenueRecognized	0	USD
CY2020	ati	Contractwith Customer Liability Noncurrent Revenue Recognized ContractwithCustomerLiabilityNoncurrentRevenueRecognized	0	USD
CY2019	ati	Contractwith Customer Liability Noncurrent Revenue Recognized ContractwithCustomerLiabilityNoncurrentRevenueRecognized	0	USD
CY2021	ati	Contractwith Customer Liability Noncurrent Reclassification ContractwithCustomerLiabilityNoncurrentReclassification	3200000	USD
CY2020	ati	Contractwith Customer Liability Noncurrent Reclassification ContractwithCustomerLiabilityNoncurrentReclassification	7800000	USD
CY2019	ati	Contractwith Customer Liability Noncurrent Reclassification ContractwithCustomerLiabilityNoncurrentReclassification	4500000	USD
CY2021Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	84400000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	32000000.0	USD
CY2019Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	25900000	USD
CY2021Q4	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	5200000	USD
CY2020Q4	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	5400000	USD
CY2021	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1000000	USD
CY2020	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1400000	USD
CY2019	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1400000	USD
CY2021Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	160300000	USD
CY2020Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	207600000	USD
CY2021Q4	us-gaap	Inventory Work In Process InventoryWorkInProcess	829600000	USD
CY2020Q4	us-gaap	Inventory Work In Process InventoryWorkInProcess	690700000	USD
CY2021Q4	us-gaap	Inventory Finished Goods InventoryFinishedGoods	121800000	USD
CY2020Q4	us-gaap	Inventory Finished Goods InventoryFinishedGoods	181600000	USD
CY2021Q4	us-gaap	Inventory Gross InventoryGross	1111700000	USD
CY2020Q4	us-gaap	Inventory Gross InventoryGross	1079900000	USD
CY2021Q4	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	65400000	USD
CY2020Q4	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	82800000	USD
CY2021Q4	us-gaap	Inventory Net InventoryNet	1046300000	USD
CY2020Q4	us-gaap	Inventory Net InventoryNet	997100000	USD
CY2021Q4	us-gaap	Land Land	34400000	USD
CY2020Q4	us-gaap	Land Land	34800000	USD
CY2021Q4	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	575500000	USD
CY2020Q4	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	564700000	USD
CY2021Q4	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	2870200000	USD
CY2020Q4	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	2736900000	USD
CY2021Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	3480100000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	3336400000	USD
CY2021Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	1951600000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	1867200000	USD
CY2021Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1528500000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1469200000	USD
CY2021Q4	us-gaap	Construction In Progress Gross ConstructionInProgressGross	215300000	USD
CY2020Q4	us-gaap	Construction In Progress Gross ConstructionInProgressGross	233400000	USD
CY2021	us-gaap	Goodwill Period Increase Decrease GoodwillPeriodIncreaseDecrease	-12800000	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000	USD
CY2020Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	528000000	USD
CY2021Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	528000000	USD
CY2019Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	241000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	134800000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	68900000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	156200000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	68300000	USD
CY2021	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	8000000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	8000000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	10000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	7000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	7000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	7000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	7000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	7000000	USD
CY2019Q2	ati	Number Of Facilities Sold NumberOfFacilitiesSold	2	facility
CY2021Q4	ati	Retained Earnings Equity Method Undistributed Earnings RetainedEarningsEquityMethodUndistributedEarnings	13800000	USD
CY2021Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	19000000	USD
CY2020Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	24000000.0	USD
CY2019Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	23700000	USD
CY2021	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	800000	USD
CY2020	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	900000	USD
CY2021	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	5600000	USD
CY2020	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	400000	USD
CY2021	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	0	USD
CY2020	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	-200000	USD
CY2021	ati	Asset Retirement Obligation Divestiture AssetRetirementObligationDivestiture	-200000	USD
CY2020	ati	Asset Retirement Obligation Divestiture AssetRetirementObligationDivestiture	0	USD
CY2021Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	19000000.0	USD
CY2020Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	24000000.0	USD
CY2021Q4	us-gaap	Cash Cash	222800000	USD
CY2020Q4	us-gaap	Cash Cash	158200000	USD
CY2021Q4	us-gaap	Money Market Funds At Carrying Value MoneyMarketFundsAtCarryingValue	464900000	USD
CY2020Q4	us-gaap	Money Market Funds At Carrying Value MoneyMarketFundsAtCarryingValue	487700000	USD
CY2021Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	687700000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	645900000	USD
CY2021Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	92700000	USD
CY2020Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	92800000	USD
CY2021Q4	us-gaap	Interest Payable Current InterestPayableCurrent	15200000	USD
CY2020Q4	us-gaap	Interest Payable Current InterestPayableCurrent	18000000	USD
CY2021	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	1100000	USD
CY2020	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	900000	USD
CY2021	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	100000	USD
CY2019	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	2900000	USD
CY2021	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	2900000	USD
CY2020	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	2900000	USD
CY2019	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	90700000	USD
CY2020	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-7000000.0	USD
CY2019	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-10700000	USD
CY2021	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	13800000	USD
CY2020	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	0	USD
CY2019	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	-7100000	USD
CY2021	ati	Other Asset Impairment Charges And Due From Affiliates Allowance For Credit Loss OtherAssetImpairmentChargesAndDueFromAffiliatesAllowanceForCreditLoss	0	USD
CY2020	ati	Other Asset Impairment Charges And Due From Affiliates Allowance For Credit Loss OtherAssetImpairmentChargesAndDueFromAffiliatesAllowanceForCreditLoss	2400000	USD
CY2019	ati	Other Asset Impairment Charges And Due From Affiliates Allowance For Credit Loss OtherAssetImpairmentChargesAndDueFromAffiliatesAllowanceForCreditLoss	11400000	USD
CY2021	ati	Other Other Nonoperating Income Expense OtherOtherNonoperatingIncomeExpense	300000	USD
CY2020	ati	Other Other Nonoperating Income Expense OtherOtherNonoperatingIncomeExpense	100000	USD
CY2019	ati	Other Other Nonoperating Income Expense OtherOtherNonoperatingIncomeExpense	0	USD
CY2021	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	18200000	USD
CY2020	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-1200000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	64400000	USD
CY2020	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	2500000	USD
CY2019	us-gaap	Gain Loss On Sale Of Property GainLossOnSaleOfProperty	91700000	USD
CY2021Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	20800000	USD
CY2020Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	14500000	USD
CY2021Q4	ati	Total Debt TotalDebt	1842900000	USD
CY2020Q4	ati	Total Debt TotalDebt	1567800000	USD
CY2021Q4	us-gaap	Debt Current DebtCurrent	131300000	USD
CY2020Q4	us-gaap	Debt Current DebtCurrent	17800000	USD
CY2021Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	1711600000	USD
CY2020Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	1550000000	USD
CY2021	us-gaap	Interest Expense Debt InterestExpenseDebt	97600000	USD
CY2020	us-gaap	Interest Expense Debt InterestExpenseDebt	96100000	USD
CY2019	us-gaap	Interest Expense Debt InterestExpenseDebt	104900000	USD
CY2021	us-gaap	Interest Costs Capitalized InterestCostsCapitalized	4300000	USD
CY2020	us-gaap	Interest Costs Capitalized InterestCostsCapitalized	7700000	USD
CY2019	us-gaap	Interest Costs Capitalized InterestCostsCapitalized	4700000	USD
CY2021	us-gaap	Interest Paid InterestPaid	97500000	USD
CY2020	us-gaap	Interest Paid InterestPaid	95400000	USD
CY2019	us-gaap	Interest Paid InterestPaid	105700000	USD
CY2021	us-gaap	Investment Income Interest InvestmentIncomeInterest	700000	USD
CY2020	us-gaap	Investment Income Interest InvestmentIncomeInterest	1700000	USD
CY2019	us-gaap	Investment Income Interest InvestmentIncomeInterest	5900000	USD
CY2021Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	131600000	USD
CY2021Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	19600000	USD
CY2021Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	217100000	USD
CY2021Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	454700000	USD
CY2021Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	7500000	USD
CY2021	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-65500000	USD
CY2021	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	64500000	USD
CY2020	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21500000	USD
CY2020	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	19100000	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21600000	USD
CY2019	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	20900000	USD
CY2021	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-65500000	USD
CY2020	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21500000	USD
CY2020	ati	Payment Of Capped Call Transactions Cost PaymentOfCappedCallTransactionsCost	19400000	USD
CY2019	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	5500000	USD
CY2021Q4	ati	Progress Payments Made On Behalf Of Company Paid ProgressPaymentsMadeOnBehalfOfCompanyPaid	22000000	USD
CY2022Q1	ati	Progress Payments Made On Behalf Of Company Scheduled To Be Paid ProgressPaymentsMadeOnBehalfOfCompanyScheduledToBePaid	19400000	USD
CY2021	us-gaap	Proceeds From Sale Of Other Property Plant And Equipment ProceedsFromSaleOfOtherPropertyPlantAndEquipment	16200000	USD
CY2021	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	7100000	USD
CY2020	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	3500000	USD
CY2019	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	1700000	USD
CY2021	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	3100000	USD
CY2020	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	1000000.0	USD
CY2019	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	500000	USD
CY2021	us-gaap	Operating Lease Cost OperatingLeaseCost	22700000	USD
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	20800000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	20500000	USD
CY2021	us-gaap	Short Term Lease Cost ShortTermLeaseCost	1600000	USD
CY2020	us-gaap	Short Term Lease Cost ShortTermLeaseCost	1900000	USD
CY2019	us-gaap	Short Term Lease Cost ShortTermLeaseCost	3100000	USD
CY2021	us-gaap	Variable Lease Cost VariableLeaseCost	900000	USD
CY2020	us-gaap	Variable Lease Cost VariableLeaseCost	900000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	800000	USD
CY2021	us-gaap	Sublease Income SubleaseIncome	300000	USD
CY2020	us-gaap	Sublease Income SubleaseIncome	100000	USD
CY2019	us-gaap	Sublease Income SubleaseIncome	0	USD
CY2021	us-gaap	Lease Cost LeaseCost	35100000	USD
CY2019	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	500000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	17200000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	13100000	USD
CY2020	us-gaap	Lease Cost LeaseCost	28000000.0	USD
CY2019	us-gaap	Lease Cost LeaseCost	26600000	USD
CY2021	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	3000000.0	USD
CY2020	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	1000000.0	USD
CY2021	us-gaap	Operating Lease Payments OperatingLeasePayments	20000000.0	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	21700000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	20800000	USD
CY2021	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	14300000	USD
CY2020	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	6200000	USD
CY2019	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	2400000	USD
CY2021	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	58900000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	42300000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	14100000	USD
CY2021	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	4800000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	12400000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	35900000	USD
CY2021Q4	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P5Y
CY2020Q4	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P4Y
CY2019Q4	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P4Y
CY2021Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P5Y
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P6Y
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P6Y
CY2021Q4	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.052
CY2020Q4	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.062
CY2019Q4	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.053
CY2021Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.065
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.069
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.070
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	9800000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	66000000.0	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	7900000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	5600000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	12400000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	11600000	USD
CY2021Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	54400000	USD
CY2021Q4	us-gaap	Finance Lease Liability Payments Due Next Twelve Months FinanceLeaseLiabilityPaymentsDueNextTwelveMonths	23400000	USD
CY2021Q4	us-gaap	Finance Lease Liability Payments Due Year Two FinanceLeaseLiabilityPaymentsDueYearTwo	22500000	USD
CY2021Q4	us-gaap	Finance Lease Liability Payments Due Year Three FinanceLeaseLiabilityPaymentsDueYearThree	18900000	USD
CY2021Q4	us-gaap	Finance Lease Liability Payments Due Year Four FinanceLeaseLiabilityPaymentsDueYearFour	14400000	USD
CY2021Q4	us-gaap	Finance Lease Liability Payments Due Year Five FinanceLeaseLiabilityPaymentsDueYearFive	7700000	USD
CY2021Q4	us-gaap	Finance Lease Liability Payments Due After Year Five FinanceLeaseLiabilityPaymentsDueAfterYearFive	8500000	USD
CY2021Q4	us-gaap	Finance Lease Liability Payments Due FinanceLeaseLiabilityPaymentsDue	95400000	USD
CY2021Q4	us-gaap	Finance Lease Liability Undiscounted Excess Amount FinanceLeaseLiabilityUndiscountedExcessAmount	10800000	USD
CY2021Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	84600000	USD
CY2021	ati	Percentage Of Raw Material Usage Hedged PercentageOfRawMaterialUsageHedged	0.10
CY2021Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	7600000	USD
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	4800000	USD
CY2021Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	2700000	USD
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	4000000.0	USD
CY2021	us-gaap	Cash Flow Hedge Gain Loss To Be Reclassified Within Twelve Months CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths	5200000	USD
CY2019Q4	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	6000000	USD
CY2020Q4	ati	Defined Contribution Plan Deferred Contributions Due To Covid19 Pandemic DefinedContributionPlanDeferredContributionsDueToCOVID19Pandemic	7300000	USD
CY2021	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	20400000	USD
CY2020	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	29900000	USD
CY2019	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	44800000	USD
CY2020	us-gaap	Defined Benefit Plan Cost Of Providing Special Or Contractual Termination Benefit Recognized During Period DefinedBenefitPlanCostOfProvidingSpecialOrContractualTerminationBenefitRecognizedDuringPeriod	17400000	USD
CY2021	ati	Projected Retirement Benefit Expense In Next Year ProjectedRetirementBenefitExpenseInNextYear	37000000	USD
CY2021Q4	us-gaap	Defined Benefit Plan Expected Amortization Of Prior Service Cost Credit Next Fiscal Year DefinedBenefitPlanExpectedAmortizationOfPriorServiceCostCreditNextFiscalYear	-500000	USD
CY2021Q4	us-gaap	Defined Benefit Plan Expected Amortization Of Gain Loss Next Fiscal Year DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear	-77300000	USD
CY2021Q4	us-gaap	Defined Benefit Plan Expected Amortization Next Fiscal Year DefinedBenefitPlanExpectedAmortizationNextFiscalYear	76800000	USD
CY2021	ati	Multiemployer Plans Withdrawal Obligation Payment Period MultiemployerPlansWithdrawalObligationPaymentPeriod	P20Y
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1133800000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-136900000	USD
CY2019	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-69000000.0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-67900000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1201700000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-80200000	USD
CY2020	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-58300000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-21900000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1223600000	USD
CY2021	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	120600000	USD
CY2021	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-111300000	USD
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	231900000	USD
CY2021Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-991700000	USD
CY2018Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	11100000	USD
CY2019	ati	Other Comprehensive Income Lossbefore Reclassifications Netof Tax Attributableto Noncontrolling Interest OtherComprehensiveIncomeLossbeforeReclassificationsNetofTaxAttributabletoNoncontrollingInterest	-1300000	USD
CY2019	ati	Reclassificationfrom Accumulated Other Comprehensive Income Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	-1300000	USD
CY2019Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	9800000	USD
CY2020	ati	Other Comprehensive Income Lossbefore Reclassifications Netof Tax Attributableto Noncontrolling Interest OtherComprehensiveIncomeLossbeforeReclassificationsNetofTaxAttributabletoNoncontrollingInterest	11400000	USD
CY2020	ati	Reclassificationfrom Accumulated Other Comprehensive Income Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	11400000	USD
CY2020Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	21200000	USD
CY2021	ati	Other Comprehensive Income Lossbefore Reclassifications Netof Tax Attributableto Noncontrolling Interest OtherComprehensiveIncomeLossbeforeReclassificationsNetofTaxAttributabletoNoncontrollingInterest	4800000	USD
CY2021	ati	Reclassificationfrom Accumulated Other Comprehensive Income Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	USD
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	4800000	USD
CY2021Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	26000000.0	USD
CY2021	us-gaap	Other Comprehensive Income Finalization Of Pension And Non Pension Postretirement Plan Valuation Tax OtherComprehensiveIncomeFinalizationOfPensionAndNonPensionPostretirementPlanValuationTax	6400000	USD
CY2019Q4	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	6000000	USD
CY2021Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	3500000	shares
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	-42100000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	-1505400000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	185100000	USD
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	52700000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	23500000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	51400000	USD
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	10600000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-1481900000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	236500000	USD
CY2021	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	700000	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	600000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	2200000	USD
CY2021	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	-300000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	-1100000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	200000	USD
CY2021	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	9400000	USD
CY2020	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	6700000	USD
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	8100000	USD
CY2021	ati	Effective Income Tax Rate Reconciliation Restructuring EffectiveIncomeTaxRateReconciliationRestructuring	0	USD
CY2020	ati	Effective Income Tax Rate Reconciliation Restructuring EffectiveIncomeTaxRateReconciliationRestructuring	0	USD
CY2021	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	9800000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	6200000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	10500000	USD
CY2021	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	18600000	USD
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	26600000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-4600000	USD
CY2021	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-900000	USD
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	47100000	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-40400000	USD
CY2021	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-700000	USD
CY2020	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-2200000	USD
CY2019	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	6000000.0	USD
CY2021	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	17000000.0	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	71500000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-39000000.0	USD
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26800000	USD
CY2020	us-gaap	Income Tax Reconciliation Repatriation Of Foreign Earnings IncomeTaxReconciliationRepatriationOfForeignEarnings	200000	USD
CY2019	us-gaap	Income Tax Reconciliation Repatriation Of Foreign Earnings IncomeTaxReconciliationRepatriationOfForeignEarnings	3500000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	77700000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-28500000	USD
CY2021	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	2200000	USD
CY2020	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	-311200000	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	49700000	USD
CY2021	us-gaap	Income Tax Reconciliation Nondeductible Expense Impairment Losses IncomeTaxReconciliationNondeductibleExpenseImpairmentLosses	2600000	USD
CY2020	us-gaap	Income Tax Reconciliation Nondeductible Expense Impairment Losses IncomeTaxReconciliationNondeductibleExpenseImpairmentLosses	50400000	USD
CY2019	us-gaap	Income Tax Reconciliation Nondeductible Expense Impairment Losses IncomeTaxReconciliationNondeductibleExpenseImpairmentLosses	0	USD
CY2021	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	400000	USD
CY2020	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	-200000	USD
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	300000	USD
CY2021	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	17600000	USD
CY2020	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	335500000	USD
CY2019	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	-89100000	USD
CY2021	us-gaap	Income Tax Reconciliation Repatriation Of Foreign Earnings IncomeTaxReconciliationRepatriationOfForeignEarnings	2000000.0	USD
CY2019	ati	Effective Income Tax Rate Reconciliation Restructuring EffectiveIncomeTaxRateReconciliationRestructuring	4200000	USD
CY2021	ati	Effective Income Tax Rate Reconciliation Recognition Of Stranded Deferred Tax Balance EffectiveIncomeTaxRateReconciliationRecognitionOfStrandedDeferredTaxBalance	3900000	USD
CY2020	ati	Effective Income Tax Rate Reconciliation Recognition Of Stranded Deferred Tax Balance EffectiveIncomeTaxRateReconciliationRecognitionOfStrandedDeferredTaxBalance	0	USD
CY2019	ati	Effective Income Tax Rate Reconciliation Recognition Of Stranded Deferred Tax Balance EffectiveIncomeTaxRateReconciliationRecognitionOfStrandedDeferredTaxBalance	0	USD
CY2021	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	3000000.0	USD
CY2020	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	1700000	USD
CY2019	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	2700000	USD
CY2021	ati	Effective Income Tax Rate Reconciliation Withholding Taxes EffectiveIncomeTaxRateReconciliationWithholdingTaxes	3400000	USD
CY2020	ati	Effective Income Tax Rate Reconciliation Withholding Taxes EffectiveIncomeTaxRateReconciliationWithholdingTaxes	2100000	USD
CY2019	ati	Effective Income Tax Rate Reconciliation Withholding Taxes EffectiveIncomeTaxRateReconciliationWithholdingTaxes	2700000	USD
CY2021	us-gaap	Income Tax Reconciliation Tax Holidays IncomeTaxReconciliationTaxHolidays	6200000	USD
CY2020	us-gaap	Income Tax Reconciliation Tax Holidays IncomeTaxReconciliationTaxHolidays	4600000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Holidays IncomeTaxReconciliationTaxHolidays	4100000	USD
CY2021	us-gaap	Income Tax Reconciliation Other Reconciling Items IncomeTaxReconciliationOtherReconcilingItems	-2100000	USD
CY2020	us-gaap	Income Tax Reconciliation Other Reconciling Items IncomeTaxReconciliationOtherReconcilingItems	3800000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Reconciling Items IncomeTaxReconciliationOtherReconcilingItems	1600000	USD
CY2021	ati	Effective Income Tax Rate Reconciliation Recognition Of Stranded Deferred Tax Balance EffectiveIncomeTaxRateReconciliationRecognitionOfStrandedDeferredTaxBalance	3900000	USD
CY2021Q4	ati	Discrete Tax Effects Related To Postretirement Medical Benefits Settlement Gain Portion Within Valuation Allowance DiscreteTaxEffectsRelatedToPostretirementMedicalBenefitsSettlementGainPortionWithinValuationAllowance	11600000	USD
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26800000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	77700000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-28500000	USD
CY2021	us-gaap	Income Tax Reconciliation Nondeductible Expense Impairment Losses IncomeTaxReconciliationNondeductibleExpenseImpairmentLosses	2600000	USD
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$ATI
ATI INC Stock $ati

2021 Q4 Form 10-K Financial Statement

#000162828022003961 Filed on February 25, 2022

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ATI ATI INC Stock $ati

2021 Q4 Form 10-K Financial Statement

#000162828022003961 Filed on February 25, 2022

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ATI
ATI INC Stock $ati