$ATI
ATI INC Stock $ati

$ati Overview Financials Valuation SEC Filings Company Website

2021 Q4 Form 10-Q Financial Statement

#000162828021021098 Filed on November 02, 2021

Income Statement

Concept	2021 Q4	2021 Q3	2020 Q4
Revenue	$765.4M	$725.7M	$658.3M
YoY Change	16.27%	21.35%	-35.37%
Cost Of Revenue	$643.2M	$643.2M	$613.1M
YoY Change	4.91%	14.88%	-27.81%
Gross Profit	$122.2M	$82.50M	$45.20M
YoY Change	170.35%	116.54%	-73.3%
Gross Profit Margin	15.97%	11.37%	6.87%
Selling, General & Admin	$57.80M	$54.90M	$52.80M
YoY Change	9.47%	20.93%	-20.36%
% of Gross Profit	47.3%	66.55%	116.81%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$35.90M	$35.60M	$35.00M
YoY Change	2.57%	0.56%	-4.11%
% of Gross Profit	29.38%	43.15%	77.43%
Operating Expenses	$57.80M	$54.90M	$52.80M
YoY Change	9.47%	20.93%	-20.36%
Operating Profit	$64.40M	$29.90M	-$7.600M
YoY Change	-947.37%	-411.46%	-107.38%
Interest Expense	-$25.00M	-$24.70M	-$26.10M
YoY Change	-4.21%	-5.36%	0.0%
% of Operating Profit	-38.82%	-82.61%
Other Income/Expense, Net	-$6.500M	$14.50M	-$28.20M
YoY Change	-76.95%	-3725.0%	54.1%
Pretax Income	-$29.30M	$77.20M	-$1.143B
YoY Change	-97.44%	-267.1%	-5490.57%
Income Tax	-$4.700M	$22.00M	-$26.50M
% Of Pretax Income		28.5%
Net Earnings	-$29.80M	$48.70M	-$1.121B
YoY Change	-97.34%	-197.21%	-2084.07%
Net Earnings / Revenue	-3.89%	6.71%	-170.29%
Basic Earnings Per Share		$0.38	-$8.85
Diluted Earnings Per Share	-$233.9K	$0.35	-$8.85
COMMON SHARES
Basic Shares Outstanding	127.2M shares	127.2M shares	126.8M shares
Diluted Shares Outstanding		152.6M shares

Balance Sheet

Concept	2021 Q4	2021 Q3	2020 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments	$687.7M	$1.007B	$645.9M
YoY Change	6.47%	75.95%	31.6%
Cash & Equivalents	$687.7M	$1.007B	$645.9M
Short-Term Investments
Other Short-Term Assets	$48.80M	$68.80M	$38.30M
YoY Change	27.42%	41.86%	-40.44%
Inventory	$1.046B	$1.056B	$997.1M
Prepaid Expenses
Receivables	$470.0M	$502.0M	$345.8M
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$2.307B	$2.689B	$2.066B
YoY Change	11.65%	28.89%	-10.29%
LONG-TERM ASSETS
Property, Plant & Equipment	$1.529B	$1.488B	$1.469B
YoY Change	4.04%	-39.69%	-40.04%
Goodwill	$227.9M	$229.0M	$240.7M
YoY Change	-5.32%	-3.94%	-54.22%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets	$222.1M	$220.8M	$259.0M
YoY Change	-14.25%	-19.0%	-27.19%
Total Long-Term Assets	$1.979B	$1.937B	$1.969B
YoY Change	0.49%	-34.93%	-40.9%
TOTAL ASSETS
Total Short-Term Assets	$2.307B	$2.689B	$2.066B
Total Long-Term Assets	$1.979B	$1.937B	$1.969B
Total Assets	$4.285B	$4.627B	$4.035B
YoY Change	6.2%	-8.64%	-28.39%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$375.5M	$290.7M	$290.6M
YoY Change	29.22%	20.77%	-44.24%
Accrued Expenses	$233.4M	$223.0M	$233.1M
YoY Change	0.13%	4.69%	-1.98%
Deferred Revenue	$116.2M	$86.70M	$111.8M
YoY Change	3.94%	-11.35%	42.06%
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due	$131.3M	$606.9M	$17.80M
YoY Change	637.64%	4874.59%	54.78%
Total Short-Term Liabilities	$856.4M	$1.207B	$653.3M
YoY Change	31.09%	114.17%	-23.07%
LONG-TERM LIABILITIES
Long-Term Debt	$1.712B	$1.684B	$1.550B
YoY Change	10.43%	10.11%	11.72%
Other Long-Term Liabilities	$211.0M	$220.1M	$189.9M
YoY Change	11.11%	3.67%	18.1%
Total Long-Term Liabilities	$211.0M	$220.1M	$189.9M
YoY Change	11.11%	3.67%	18.1%
TOTAL LIABILITIES
Total Short-Term Liabilities	$856.4M	$1.207B	$653.3M
Total Long-Term Liabilities	$211.0M	$220.1M	$189.9M
Total Liabilities	$3.453B	$3.946B	$3.394B
YoY Change	1.74%	22.78%	-1.39%
SHAREHOLDERS EQUITY
Retained Earnings	$72.70M	$102.5M	$106.5M
YoY Change	-31.74%	-91.65%	-93.66%
Common Stock	$1.609B	$1.605B	$1.638B
YoY Change	-1.76%	-1.84%	0.46%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$4.800M	$4.800M	$0.00
YoY Change			-100.0%
Treasury Stock Shares	231.9K shares	229.3K shares	2.672K shares
Shareholders Equity	$685.6M	$541.4M	$521.1M
YoY Change
Total Liabilities & Shareholders Equity	$4.285B	$4.627B	$4.035B
YoY Change	6.2%	-8.64%	-28.39%

Cashflow Statement

Concept	2021 Q4	2021 Q3	2020 Q4
OPERATING ACTIVITIES
Net Income	-$29.80M	$48.70M	-$1.121B
YoY Change	-97.34%	-197.21%	-2084.07%
Depreciation, Depletion And Amortization	$35.90M	$35.60M	$35.00M
YoY Change	2.57%	0.56%	-4.11%
Cash From Operating Activities	$260.9M	-$142.2M	$121.9M
YoY Change	114.03%	-339.39%	-49.23%
INVESTING ACTIVITIES
Capital Expenditures	-$48.40M	-$42.80M	-$41.90M
YoY Change	15.51%	49.65%	-40.23%
Acquisitions
YoY Change
Other Investing Activities	$19.60M	$53.10M	$2.400M
YoY Change	716.67%	4325.0%	0.0%
Cash From Investing Activities	-$28.80M	$10.30M	-$39.50M
YoY Change	-27.09%	-137.59%	-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	666.2M	-8.700M
YoY Change	6235.63%	60463.64%	-95.49%
NET CHANGE
Cash From Operating Activities	260.9M	-142.2M	121.9M
Cash From Investing Activities	-28.80M	10.30M	-39.50M
Cash From Financing Activities	-551.2M	666.2M	-8.700M
Net Change In Cash	-319.1M	534.3M	73.70M
YoY Change	-532.97%	1514.2%	-459.51%
FREE CASH FLOW
Cash From Operating Activities	$260.9M	-$142.2M	$121.9M
Capital Expenditures	-$48.40M	-$42.80M	-$41.90M
Free Cash Flow	$309.3M	-$99.40M	$163.8M
YoY Change	88.83%	-212.95%	-47.2%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
	dei	Amendment Flag AmendmentFlag	false
	dei	Entity Central Index Key EntityCentralIndexKey	0001018963
	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2021
	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	Q3
	dei	Document Type DocumentType	10-Q
	dei	Document Quarterly Report DocumentQuarterlyReport	true
	dei	Document Period End Date DocumentPeriodEndDate	2021-09-30
	dei	Document Transition Report DocumentTransitionReport	false
	dei	Entity File Number EntityFileNumber	1-12001
	dei	Entity Registrant Name EntityRegistrantName	ALLEGHENY TECHNOLOGIES INCORPORATED
	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	25-1792394
	dei	Entity Address Address Line1 EntityAddressAddressLine1	1000 Six PPG Place
	dei	Entity Address City Or Town EntityAddressCityOrTown	Pittsburgh,
	dei	Entity Address State Or Province EntityAddressStateOrProvince	PA
	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	15222-5479
	dei	City Area Code CityAreaCode	412
	dei	Local Phone Number LocalPhoneNumber	394-2800
	dei	Security12b Title Security12bTitle	Common stock, par value $0.10
	dei	Trading Symbol TradingSymbol	ATI
	dei	Security Exchange Name SecurityExchangeName	NYSE
	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
	dei	Entity Small Business EntitySmallBusiness	false
	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
	dei	Entity Shell Company EntityShellCompany	false
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CY2021Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	1006800000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	645900000	USD
CY2021Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	502000000.0	USD
CY2020Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	345800000	USD
CY2021Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	55700000	USD
CY2020Q4	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	38900000	USD
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CY2020Q4	us-gaap	Inventory Net InventoryNet	997100000	USD
CY2021Q3	us-gaap	Other Assets Current OtherAssetsCurrent	68800000	USD
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CY2020Q3	ati	Interest Expense Net InterestExpenseNet	25100000	USD
	ati	Interest Expense Net InterestExpenseNet	72200000	USD
	ati	Interest Expense Net InterestExpenseNet	68700000	USD
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	us-gaap	Profit Loss ProfitLoss	-443300000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-5000000.0	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	23200000	USD
	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-2800000	USD
	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	14000000.0	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	6700000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	6100000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	14100000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	-4200000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	3000000.0	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	-400000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	6200000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	-6400000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	0	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	0	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	0	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	0	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	3700000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	6500000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	7900000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	2200000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-22500000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-21300000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-66900000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-63900000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	-400000	USD
CY2020Q3	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	-800000	USD
	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	-1400000	USD
	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	-2300000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	-21900000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	0	USD
	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	-21900000	USD
	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	0	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	15500000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	0	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	15500000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	0	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-15700000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-20500000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-59100000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-61600000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	14400000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	50200000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	64200000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	77800000	USD
CY2021Q3	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	69600000	USD
CY2020Q3	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	3200000	USD
	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	72600000	USD
	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	-365500000	USD
CY2021Q3	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	5700000	USD
CY2020Q3	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	9100000	USD
	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	18500000	USD
	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	13000000.0	USD
CY2021Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	63900000	USD
CY2020Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-5900000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	54100000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-378500000	USD
	us-gaap	Profit Loss ProfitLoss	8400000	USD
	us-gaap	Profit Loss ProfitLoss	-443300000	USD
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	108000000.0	USD
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	108300000	USD
	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	1900000	USD
	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	98500000	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000.0	USD
	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21500000	USD
	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	2500000	USD
	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	3300000	USD
	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	13700000	USD
	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	0	USD
	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	63400000	USD
	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-119300000	USD
	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	158000000.0	USD
	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-166200000	USD
	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	600000	USD
	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	-280500000	USD
	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	-112900000	USD
	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	-78300000	USD
	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	13200000	USD
	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-49600000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	-244800000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	45000000.0	USD
	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	104200000	USD
	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	94600000	USD
	us-gaap	Proceeds From Divestiture Of Businesses ProceedsFromDivestitureOfBusinesses	53000000.0	USD
	us-gaap	Proceeds From Divestiture Of Businesses ProceedsFromDivestitureOfBusinesses	0	USD
	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	2900000	USD
	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	4000000.0	USD
	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	200000	USD
	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-1400000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-48500000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-89200000	USD
	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	675700000	USD
	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	391400000	USD
	us-gaap	Repayments Of Long Term Debt And Capital Securities RepaymentsOfLongTermDebtAndCapitalSecurities	11000000.0	USD
	us-gaap	Repayments Of Long Term Debt And Capital Securities RepaymentsOfLongTermDebtAndCapitalSecurities	209500000	USD
	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	3600000	USD
	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	-900000	USD
	ati	Payment Of Capped Call Transactions Cost PaymentOfCappedCallTransactionsCost	0	USD
	ati	Payment Of Capped Call Transactions Cost PaymentOfCappedCallTransactionsCost	19400000	USD
	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	9300000	USD
	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	9100000	USD
	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	0	USD
	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	19100000	USD
	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	4800000	USD
	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	7800000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	654200000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	125600000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	360900000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	81400000	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
CY2021Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1006800000	USD
CY2020Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	572200000	USD
CY2020Q2	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1842300000	USD
CY2020Q3	us-gaap	Profit Loss ProfitLoss	-47000000.0	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	50200000	USD
CY2020Q3	us-gaap	Adjustments To Additional Paid In Capital Equity Component Of Convertible Debt AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebt	1100000	USD
CY2020Q3	ati	Adjustments To Additional Paid In Capital Convertible Note Capped Call AdjustmentsToAdditionalPaidInCapitalConvertibleNoteCappedCall	400000	USD
CY2020Q3	ati	Employee Stock Plans EmployeeStockPlans	-3600000	USD
CY2020Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1849800000	USD
CY2021Q2	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	606100000	USD
CY2021Q3	us-gaap	Profit Loss ProfitLoss	55200000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	14400000	USD
CY2021Q3	ati	Employee Stock Plans EmployeeStockPlans	-4500000	USD
CY2021Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	680200000	USD
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	2193200000	USD
	us-gaap	Profit Loss ProfitLoss	-443300000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	77800000	USD
	us-gaap	Adjustments To Additional Paid In Capital Equity Component Of Convertible Debt AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebt	49800000	USD
	ati	Adjustments To Additional Paid In Capital Convertible Note Capped Call AdjustmentsToAdditionalPaidInCapitalConvertibleNoteCappedCall	19400000	USD
	ati	Employee Stock Plans EmployeeStockPlans	8300000	USD
CY2020Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1849800000	USD
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	641400000	USD
	us-gaap	Profit Loss ProfitLoss	8400000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	64200000	USD
	ati	Employee Stock Plans EmployeeStockPlans	-11600000	USD
CY2021Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	680200000	USD
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2021Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	725700000	USD
CY2020Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	598000000.0	USD
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2034400000	USD
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2323800000	USD
CY2021Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	725700000	USD
CY2020Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	598000000.0	USD
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2034400000	USD
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2323800000	USD
CY2021Q3	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
CY2020Q3	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
CY2021Q3	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	1700000000	USD
CY2020Q3	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	1400000000	USD
CY2021Q3	ati	Revenue Remaining Performance Obligation Current RevenueRemainingPerformanceObligationCurrent	0.80	USD
CY2021Q3	ati	Accountsreceivablewithcustomers Accountsreceivablewithcustomers	506100000	USD
CY2020Q4	ati	Accountsreceivablewithcustomers Accountsreceivablewithcustomers	350100000	USD
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	4300000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	4600000	USD
	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	400000	USD
	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	100000	USD
	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	600000	USD
	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	400000	USD
CY2021Q3	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	4100000	USD
CY2020Q3	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	4300000	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
	ati	Contractwith Customer Asset Current Period Increase ContractwithCustomerAssetCurrentPeriodIncrease	74300000	USD
	ati	Contractwith Customer Asset Current Period Increase ContractwithCustomerAssetCurrentPeriodIncrease	55800000	USD
	ati	Contractwith Customer Asset Current Reclassifiedto Receivable ContractwithCustomerAssetCurrentReclassifiedtoReceivable	49000000.0	USD
	ati	Contractwith Customer Asset Current Reclassifiedto Receivable ContractwithCustomerAssetCurrentReclassifiedtoReceivable	52700000	USD
	ati	Contractwith Customer Asset Current Impairment ContractwithCustomerAssetCurrentImpairment	0	USD
	ati	Contractwith Customer Asset Current Impairment ContractwithCustomerAssetCurrentImpairment	0	USD
	ati	Contractwith Customer Asset Current Reclassification ContractwithCustomerAssetCurrentReclassification	8500000	USD
	ati	Contractwith Customer Asset Current Reclassification ContractwithCustomerAssetCurrentReclassification	-100000	USD
CY2021Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	55700000	USD
CY2020Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	41700000	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
	ati	Contractwith Customer Asset Nocurrent Period Increase ContractwithCustomerAssetNocurrentPeriodIncrease	0	USD
	ati	Contractwith Customer Asset Nocurrent Period Increase ContractwithCustomerAssetNocurrentPeriodIncrease	0	USD
	ati	Contractwith Customer Asset Noncurrent Reclassifiedto Receivable ContractwithCustomerAssetNoncurrentReclassifiedtoReceivable	0	USD
	ati	Contractwith Customer Asset Noncurrent Reclassifiedto Receivable ContractwithCustomerAssetNoncurrentReclassifiedtoReceivable	0	USD
	ati	Contractwith Customer Asset Noncurrent Impairment ContractwithCustomerAssetNoncurrentImpairment	0	USD
	ati	Contractwith Customer Asset Noncurrent Impairment ContractwithCustomerAssetNoncurrentImpairment	0	USD
	ati	Contractwith Customer Asset Noncurrent Reclassification ContractwithCustomerAssetNoncurrentReclassification	0	USD
	ati	Contractwith Customer Asset Noncurrent Reclassification ContractwithCustomerAssetNoncurrentReclassification	100000	USD
CY2021Q3	us-gaap	Contract With Customer Asset Net Noncurrent ContractWithCustomerAssetNetNoncurrent	0	USD
CY2020Q3	us-gaap	Contract With Customer Asset Net Noncurrent ContractWithCustomerAssetNetNoncurrent	0	USD
CY2020Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	111800000	USD
	ati	Contractwith Customer Liability Current Period Increase ContractwithCustomerLiabilityCurrentPeriodIncrease	102000000.0	USD
	ati	Contractwith Customer Liability Current Period Increase ContractwithCustomerLiabilityCurrentPeriodIncrease	121500000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	78700000	USD
	ati	Contractwith Customer Liability Current Reclassifiedto Revenue ContractwithCustomerLiabilityCurrentReclassifiedtoRevenue	-74400000	USD
	ati	Contractwith Customer Liability Current Reclassifiedto Revenue ContractwithCustomerLiabilityCurrentReclassifiedtoRevenue	-42900000	USD
	ati	Contractwith Customer Liability Current Revenue Recognized ContractwithCustomerLiabilityCurrentRevenueRecognized	-46200000	USD
	ati	Contractwith Customer Liability Current Revenue Recognized ContractwithCustomerLiabilityCurrentRevenueRecognized	-65600000	USD
	ati	Contract With Customer Liability Current Divestiture ContractWithCustomerLiabilityCurrentDivestiture	-800000	USD
	ati	Contract With Customer Liability Current Divestiture ContractWithCustomerLiabilityCurrentDivestiture	0	USD
	ati	Contractwith Customer Liability Current Other ContractwithCustomerLiabilityCurrentOther	200000	USD
	ati	Contractwith Customer Liability Current Other ContractwithCustomerLiabilityCurrentOther	0	USD
	ati	Contractwith Customer Liability Current Reclassification ContractwithCustomerLiabilityCurrentReclassification	5900000	USD
	ati	Contractwith Customer Liability Current Reclassification ContractwithCustomerLiabilityCurrentReclassification	-6100000	USD
CY2021Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	86700000	USD
CY2020Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	97800000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	32000000.0	USD
CY2019Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	25900000	USD
	ati	Contractwith Customer Liability Noncurrent Period Increase ContractwithCustomerLiabilityNoncurrentPeriodIncrease	45400000	USD
	ati	Contractwith Customer Liability Noncurrent Period Increase ContractwithCustomerLiabilityNoncurrentPeriodIncrease	12900000	USD
	ati	Contractwith Customer Liability Noncurrent Reclassifiedto Revenue ContractwithCustomerLiabilityNoncurrentReclassifiedtoRevenue	-800000	USD
	ati	Contractwith Customer Liability Noncurrent Reclassifiedto Revenue ContractwithCustomerLiabilityNoncurrentReclassifiedtoRevenue	-800000	USD
	ati	Contractwith Customer Liability Noncurrent Revenue Recognized ContractwithCustomerLiabilityNoncurrentRevenueRecognized	0	USD
	ati	Contractwith Customer Liability Noncurrent Revenue Recognized ContractwithCustomerLiabilityNoncurrentRevenueRecognized	0	USD
	ati	Contractwith Customer Liability Noncurrent Other ContractwithCustomerLiabilityNoncurrentOther	0	USD
	ati	Contractwith Customer Liability Noncurrent Other ContractwithCustomerLiabilityNoncurrentOther	0	USD
	ati	Contractwith Customer Liability Noncurrent Reclassification ContractwithCustomerLiabilityNoncurrentReclassification	2600000	USD
	ati	Contractwith Customer Liability Noncurrent Reclassification ContractwithCustomerLiabilityNoncurrentReclassification	6100000	USD
CY2021Q3	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	74000000.0	USD
CY2020Q3	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	31900000	USD
CY2021Q3	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	5300000	USD
CY2020Q4	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	5400000	USD
CY2021Q3	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	200000	USD
	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	700000	USD
CY2020Q3	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	400000	USD
	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1100000	USD
CY2021Q3	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	195500000	USD
CY2020Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	207600000	USD
CY2021Q3	us-gaap	Inventory Work In Process InventoryWorkInProcess	804000000.0	USD
CY2020Q4	us-gaap	Inventory Work In Process InventoryWorkInProcess	690700000	USD
CY2021Q3	us-gaap	Inventory Finished Goods InventoryFinishedGoods	125100000	USD
CY2020Q4	us-gaap	Inventory Finished Goods InventoryFinishedGoods	181600000	USD
CY2021Q3	us-gaap	Inventory Gross InventoryGross	1124600000	USD
CY2020Q4	us-gaap	Inventory Gross InventoryGross	1079900000	USD
CY2021Q3	us-gaap	Inventory Lifo Reserve InventoryLIFOReserve	-300000	USD
CY2020Q4	us-gaap	Inventory Lifo Reserve InventoryLIFOReserve	-44100000	USD
CY2021Q3	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	69100000	USD
CY2020Q4	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	126900000	USD
CY2021Q3	us-gaap	Inventory Net InventoryNet	1055800000	USD
CY2020Q4	us-gaap	Inventory Net InventoryNet	997100000	USD
	us-gaap	Inventory Lifo Reserve Period Charge InventoryLIFOReservePeriodCharge	43800000	USD
	us-gaap	Inventory Lifo Reserve Period Charge InventoryLIFOReservePeriodCharge	-7500000	USD
	ati	Inventory Net Realizable Value Reserve Period Charge InventoryNetRealizableValueReservePeriodCharge	-43800000	USD
	ati	Inventory Net Realizable Value Reserve Period Charge InventoryNetRealizableValueReservePeriodCharge	7500000	USD
	ati	Lifo Provision Benefitand Changein Debit Lifonr Vreservenet LifoProvisionBenefitandChangeinDebitLIFONRVreservenet	0	USD
	ati	Lifo Provision Benefitand Changein Debit Lifonr Vreservenet LifoProvisionBenefitandChangeinDebitLIFONRVreservenet	0	USD
CY2021Q3	us-gaap	Land Land	34900000	USD
CY2020Q4	us-gaap	Land Land	34800000	USD
CY2021Q3	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	572100000	USD
CY2020Q4	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	564700000	USD
CY2021Q3	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	2804900000	USD
CY2020Q4	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	2736900000	USD
CY2021Q3	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	3411900000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	3336400000	USD
CY2021Q3	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	1924300000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	1867200000	USD
CY2021Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1487600000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1469200000	USD
CY2021Q3	us-gaap	Construction In Progress Gross ConstructionInProgressGross	214800000	USD
CY2021Q3	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	200000	USD
CY2020Q3	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	100000	USD
	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	700000	USD
	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	600000	USD
CY2021Q3	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	100000	USD
CY2020Q3	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	800000	USD
CY2021Q3	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	400000	USD
	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	2500000	USD
	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	3300000	USD
CY2020Q3	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-1000000.0	USD
	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	400000	USD
	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-6600000	USD
CY2021Q3	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	13700000	USD
CY2020Q3	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	0	USD
	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	13700000	USD
	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	0	USD
CY2021Q3	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	0	USD
CY2020Q3	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	0	USD
	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	0	USD
	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	4300000	USD
CY2021Q3	ati	Other Nonoperating Income Expense Other OtherNonoperatingIncomeExpenseOther	100000	USD
CY2020Q3	ati	Other Nonoperating Income Expense Other OtherNonoperatingIncomeExpenseOther	-300000	USD
	ati	Other Nonoperating Income Expense Other OtherNonoperatingIncomeExpenseOther	100000	USD
	ati	Other Nonoperating Income Expense Other OtherNonoperatingIncomeExpenseOther	0	USD
CY2021Q3	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	14500000	USD
CY2020Q3	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-400000	USD
	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	17400000	USD
	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-800000	USD
	us-gaap	Gain Loss On Sale Of Property GainLossOnSaleOfProperty	2500000	USD
	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	4300000	USD
CY2021Q3	us-gaap	Restructuring Charges RestructuringCharges	-2300000	USD
CY2021Q3	ati	Restructuring And Related Costs Number Of Positions With Decreased Severance Related Reserve RestructuringAndRelatedCostsNumberOfPositionsWithDecreasedSeveranceRelatedReserve	50	employee
	us-gaap	Restructuring Charges RestructuringCharges	-8500000	USD
	ati	Restructuring And Related Costs Number Of Positions With Decreased Severance Related Reserve RestructuringAndRelatedCostsNumberOfPositionsWithDecreasedSeveranceRelatedReserve	250	employee
CY2020Q3	us-gaap	Restructuring Charges RestructuringCharges	2300000	USD
	us-gaap	Restructuring Charges RestructuringCharges	27000000	USD
CY2020Q3	us-gaap	Restructuring And Related Cost Number Of Positions Eliminated RestructuringAndRelatedCostNumberOfPositionsEliminated	100	employee
CY2020Q2	us-gaap	Restructuring And Related Cost Number Of Positions Eliminated RestructuringAndRelatedCostNumberOfPositionsEliminated	550	employee
CY2020Q1	us-gaap	Restructuring And Related Cost Number Of Positions Eliminated RestructuringAndRelatedCostNumberOfPositionsEliminated	90	employee
CY2020Q4	us-gaap	Restructuring Reserve RestructuringReserve	43400000	USD
	us-gaap	Payments For Restructuring PaymentsForRestructuring	12400000	USD
CY2021Q3	us-gaap	Restructuring Reserve RestructuringReserve	21800000	USD
CY2021Q3	us-gaap	Restructuring Reserve RestructuringReserve	21800000	USD
CY2021Q3	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	22800000	USD
CY2020Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	14500000	USD
CY2021Q3	ati	Total Debt TotalDebt	2290500000	USD
CY2020Q4	ati	Total Debt TotalDebt	1567800000	USD
CY2021Q3	us-gaap	Debt Current DebtCurrent	606900000	USD
CY2020Q4	us-gaap	Debt Current DebtCurrent	17800000	USD
CY2021Q3	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	1683600000	USD
CY2020Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	1550000000	USD
	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21500000	USD
	ati	Percentage Of Raw Material Usage Hedged PercentageOfRawMaterialUsageHedged	0.10
	ati	Percentage Of Forecasted Natural Gas Usage Hedgedfor Year1 PercentageOfForecastedNaturalGasUsageHedgedforYear1	0.80
	ati	Percentage Of Forecasted Natural Gas Usage Hedgedfor Year2 PercentageOfForecastedNaturalGasUsageHedgedforYear2	0.75
	ati	Percentage Of Forecasted Natural Gas Usage Hedged For Year3 PercentageOfForecastedNaturalGasUsageHedgedForYear3	0.35
	ati	Percentage Of Forecasted Natural Gas Usage Year4 PercentageOfForecastedNaturalGasUsageYear4	0.05
	us-gaap	Cash Flow Hedge Gain Loss To Be Reclassified Within Twelve Months CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths	8600000	USD
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2021Q3	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	94200000	USD
CY2020Q3	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	27800000	USD
	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	241700000	USD
	ati	Segment Earnings Before Income Taxes Depreciation Amortization Ebitda SegmentEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	207600000	USD
CY2021Q3	ati	Lifo Provision Benefitand Changein Debit Lifonr Vreservenet LifoProvisionBenefitandChangeinDebitLIFONRVreservenet	0	USD
CY2020Q3	ati	Lifo Provision Benefitand Changein Debit Lifonr Vreservenet LifoProvisionBenefitandChangeinDebitLIFONRVreservenet	0	USD
	ati	Lifo Provision Benefitand Changein Debit Lifonr Vreservenet LifoProvisionBenefitandChangeinDebitLIFONRVreservenet	0	USD
	ati	Lifo Provision Benefitand Changein Debit Lifonr Vreservenet LifoProvisionBenefitandChangeinDebitLIFONRVreservenet	0	USD
CY2021Q3	ati	Corporate Expenses CorporateExpenses	12900000	USD
CY2020Q3	ati	Corporate Expenses CorporateExpenses	10200000	USD
	ati	Corporate Expenses CorporateExpenses	41000000.0	USD
	ati	Corporate Expenses CorporateExpenses	29700000	USD
CY2021Q3	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	1400000	USD
CY2020Q3	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	1000000.0	USD
	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	4500000	USD
	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	4600000	USD
CY2021Q3	ati	Adjusted Earnings Before Income Taxes Depreciation Amortization Ebitda AdjustedEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	79900000	USD
CY2020Q3	ati	Adjusted Earnings Before Income Taxes Depreciation Amortization Ebitda AdjustedEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	16600000	USD
	ati	Adjusted Earnings Before Income Taxes Depreciation Amortization Ebitda AdjustedEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	196200000	USD
	ati	Adjusted Earnings Before Income Taxes Depreciation Amortization Ebitda AdjustedEarningsBeforeIncomeTaxesDepreciationAmortizationEBITDA	173300000	USD
CY2021Q3	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	35600000	USD
CY2020Q3	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	35400000	USD
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	108000000.0	USD
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	108300000	USD
CY2021Q3	ati	Interest Expense Net InterestExpenseNet	25100000	USD
CY2020Q3	ati	Interest Expense Net InterestExpenseNet	25100000	USD
	ati	Interest Expense Net InterestExpenseNet	72200000	USD
	ati	Interest Expense Net InterestExpenseNet	68700000	USD
CY2021Q3	us-gaap	Restructuring Charges RestructuringCharges	-2300000	USD
CY2020Q3	us-gaap	Restructuring Charges RestructuringCharges	2300000	USD
	us-gaap	Restructuring Charges RestructuringCharges	-8500000	USD
	us-gaap	Restructuring Charges RestructuringCharges	27000000.0	USD
CY2021Q3	ati	Strike Related Costs StrikeRelatedCosts	22900000	USD
CY2020Q3	ati	Strike Related Costs StrikeRelatedCosts	0	USD
	ati	Strike Related Costs StrikeRelatedCosts	63200000	USD
	ati	Strike Related Costs StrikeRelatedCosts	0	USD
CY2021Q3	us-gaap	Defined Benefit Plan Recognized Net Gain Loss Due To Settlements1 DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1	64900000	USD
CY2020Q3	us-gaap	Defined Benefit Plan Recognized Net Gain Loss Due To Settlements1 DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1	0	USD
	us-gaap	Defined Benefit Plan Recognized Net Gain Loss Due To Settlements1 DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1	64900000	USD
	us-gaap	Defined Benefit Plan Recognized Net Gain Loss Due To Settlements1 DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1	0	USD
CY2021Q3	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2020Q3	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000.0	USD
CY2021Q3	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2020Q3	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21500000	USD
CY2021Q3	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	13700000	USD
CY2020Q3	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	0	USD
	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	13700000	USD
	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	2500000	USD
CY2021Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	77200000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-46200000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	39900000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-339100000	USD
CY2021Q1	ati	Entity Number Of Employees Covered By Usw Collective Bargaining Agreements That Expired February282021 EntityNumberOfEmployeesCoveredByUSWCollectiveBargainingAgreementsThatExpiredFebruary282021	1100	employee
CY2021Q3	ati	Strike Related Costs StrikeRelatedCosts	22900000	USD
	ati	Strike Related Costs StrikeRelatedCosts	63200000	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000	USD
CY2021Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	22000000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	31500000	USD
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	800000	USD
CY2020Q3	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	-0.017
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	104200000	USD
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	-0.307
CY2020Q2	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	99000000	USD
CY2021Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	48700000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	-50100000	USD
	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	-8400000	USD
	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	-451600000	USD
CY2020Q3	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	-50100000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	-8400000	USD
CY2021Q3	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	52700000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	-451600000	USD
CY2021Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	127200000	shares
CY2020Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	126600000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	127000000.0	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	126500000	shares
CY2021Q3	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	800000	shares
CY2021Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	152600000	shares
CY2020Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	126600000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	127000000.0	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	126500000	shares
CY2021Q3	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.38
CY2020Q3	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	-0.40
	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	-0.07
	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	-3.57
CY2021Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.35
CY2020Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	-0.40
	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	-0.07
	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	-3.57
CY2021Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	25600000	shares
CY2020Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	25000000	shares
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	21900000	shares
CY2021Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1176300000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	1000000.0	USD
CY2021Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-14200000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	15200000	USD
CY2021Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1161100000	USD
CY2021Q2	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	23700000	USD
CY2021Q3	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	-800000	USD
CY2021Q3	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	-800000	USD
CY2021Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	22900000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1223600000	USD
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	6100000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-56400000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	62500000	USD
CY2021Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1161100000	USD
CY2020Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	21200000	USD
	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	1700000	USD
	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	1700000	USD
CY2021Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	22900000	USD
CY2020Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1172800000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	21900000	USD
CY2020Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-22300000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	44200000	USD
CY2020Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1128600000	USD
CY2020Q2	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	8500000	USD
CY2020Q3	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	6000000.0	USD
CY2020Q3	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	6000000.0	USD
CY2020Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	14500000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1201700000	USD
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	6200000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-66900000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	73100000	USD
CY2020Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1128600000	USD
CY2019Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	9800000	USD
	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	4700000	USD
	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	4700000	USD
CY2020Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	14500000	USD
CY2021Q3	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	13000000	USD
CY2021Q3	us-gaap	Accrued Environmental Loss Contingencies Current AccruedEnvironmentalLossContingenciesCurrent	5000000	USD
CY2021Q3	ati	Environmental Remediation Obligation Federal Superfund Sites EnvironmentalRemediationObligationFederalSuperfundSites	3000000	USD
CY2021Q3	ati	Environmental Remediation Obligation For Formerly Owned Sites EnvironmentalRemediationObligationForFormerlyOwnedSites	8000000	USD
CY2021Q3	ati	Environmental Remediation Obligation For Owned Or Controlled Sites With Closed Operations EnvironmentalRemediationObligationForOwnedOrControlledSitesWithClosedOperations	2000000	USD
CY2021Q1	ati	Entity Number Of Employees Covered By Usw Collective Bargaining Agreements That Expired February282021 EntityNumberOfEmployeesCoveredByUSWCollectiveBargainingAgreementsThatExpiredFebruary282021	1100	employee
CY2021Q1	ati	Entity Number Of Employees Covered By Usw Collective Bargaining Agreements That Expired February282021 EntityNumberOfEmployeesCoveredByUSWCollectiveBargainingAgreementsThatExpiredFebruary282021	1100	employee

Files In Submission

Name	View Source	Status
0001628280-21-021098-index-headers.html	Edgar Link	pending
0001628280-21-021098-index.html	Edgar Link	pending
0001628280-21-021098.txt	Edgar Link	pending
0001628280-21-021098-xbrl.zip	Edgar Link	pending
ati-20210930.htm	Edgar Link	pending
ati-20210930.xsd	Edgar Link	pending
ati-20210930_cal.xml	Edgar Link	unprocessable
ati-20210930_def.xml	Edgar Link	unprocessable
ati-20210930_htm.xml	Edgar Link	completed
ati-20210930_lab.xml	Edgar Link	unprocessable
ati-20210930_pre.xml	Edgar Link	unprocessable
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
fy2021q3exhibit311.htm	Edgar Link	pending
fy2021q3exhibit312.htm	Edgar Link	pending
fy2021q3exhibit321.htm	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
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report.css	Edgar Link	pending
Show.js	Edgar Link	pending

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$ATI
ATI INC Stock $ati

2021 Q4 Form 10-Q Financial Statement

#000162828021021098 Filed on November 02, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ATI ATI INC Stock $ati

2021 Q4 Form 10-Q Financial Statement

#000162828021021098 Filed on November 02, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ATI
ATI INC Stock $ati