$ATI
ATI INC Stock $ati

$ati Overview Financials Valuation SEC Filings Company Website

2020 Q3 Form 10-Q Financial Statement

#000162828020015070 Filed on October 29, 2020

Income Statement

Concept	2020 Q3	2019 Q4	2019 Q3
Revenue	$598.0M	$1.019B	$1.019B
YoY Change	-41.3%	-1.86%	-0.15%
Cost Of Revenue	$559.9M	$849.3M	$859.0M
YoY Change	-34.82%	-4.61%	-0.09%
Gross Profit	$38.10M	$169.3M	$159.7M
YoY Change	-76.14%	14.7%	-0.44%
Gross Profit Margin	6.37%	16.62%	15.68%
Selling, General & Admin	$45.40M	$66.30M	$65.20M
YoY Change	-30.37%	-9.05%	-0.46%
% of Gross Profit	119.16%	39.16%	40.83%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$35.40M	$36.50M	$37.00M
YoY Change	-4.32%	-7.12%	-3.65%
% of Gross Profit	92.91%	21.56%	23.17%
Operating Expenses	$45.40M	$66.30M	$65.20M
YoY Change	-30.37%	-9.05%	-0.46%
Operating Profit	-$9.600M	$103.0M	$94.50M
YoY Change	-110.16%	37.88%	-0.42%
Interest Expense	-$26.10M	-$26.10M	-$26.60M
YoY Change	-1.88%	3.57%	7.26%
% of Operating Profit		-25.34%	-28.15%
Other Income/Expense, Net	-$400.0K	-$18.30M	$67.20M
YoY Change	-100.6%	77.67%	8300.0%
Pretax Income	-$46.20M	$21.20M	$119.0M
YoY Change	-138.82%	-45.92%	90.4%
Income Tax	$800.0K	-$38.80M	$3.700M
% Of Pretax Income		-183.02%	3.11%
Net Earnings	-$50.10M	$56.50M	$111.0M
YoY Change	-145.14%	37.47%	119.8%
Net Earnings / Revenue	-8.38%	5.55%	10.9%
Basic Earnings Per Share	-$0.40	$0.45	$0.88
Diluted Earnings Per Share	-$0.40	$0.41	$0.78
COMMON SHARES
Basic Shares Outstanding	126.6M shares	126.1M shares	126.1M shares
Diluted Shares Outstanding	126.6M shares		146.7M shares

Balance Sheet

Concept	2020 Q3	2019 Q4	2019 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments	$572.2M	$490.8M	$511.3M
YoY Change	11.91%	28.48%	233.09%
Cash & Equivalents	$572.2M	$490.8M	$511.3M
Short-Term Investments
Other Short-Term Assets	$48.50M	$64.30M	$108.1M
YoY Change	-55.13%	-13.81%	21.19%
Inventory	$1.036B	$1.155B	$1.169B
Prepaid Expenses
Receivables	$388.0M	$554.1M	$596.7M
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$2.086B	$2.303B	$2.422B
YoY Change	-13.87%	2.51%	14.13%
LONG-TERM ASSETS
Property, Plant & Equipment	$2.467B	$2.450B	$2.408B
YoY Change	2.45%	-1.01%	-2.63%
Goodwill	$238.4M	$525.8M	$523.8M
YoY Change	-54.49%	-1.66%	-2.35%
Intangibles
YoY Change
Long-Term Investments		$0.00	$0.00
YoY Change
Other Assets	$272.6M	$355.7M	$275.2M
YoY Change	-0.94%	44.95%	6.83%
Total Long-Term Assets	$2.978B	$3.332B	$3.207B
YoY Change	-7.14%	2.35%	-1.84%
TOTAL ASSETS
Total Short-Term Assets	$2.086B	$2.303B	$2.422B
Total Long-Term Assets	$2.978B	$3.332B	$3.207B
Total Assets	$5.064B	$5.635B	$5.629B
YoY Change	-10.04%	2.41%	4.45%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$240.7M	$521.2M	$415.8M
YoY Change	-42.11%	4.49%	-0.07%
Accrued Expenses	$213.0M	$237.8M	$238.3M
YoY Change	-10.62%	-8.57%	4.2%
Deferred Revenue	$97.80M	$78.70M	$97.10M
YoY Change	0.72%	10.22%	40.32%
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due	$12.20M	$11.50M	$12.10M
YoY Change	0.83%	74.24%	-27.11%
Total Short-Term Liabilities	$563.7M	$849.2M	$763.3M
YoY Change	-26.15%	1.47%	4.48%
LONG-TERM LIABILITIES
Long-Term Debt	$1.529B	$1.387B	$1.542B
YoY Change	-0.82%	-9.65%	0.42%
Other Long-Term Liabilities	$212.3M	$160.8M	$124.9M
YoY Change	69.98%	79.87%	87.26%
Total Long-Term Liabilities	$212.3M	$160.8M	$124.9M
YoY Change	69.98%	79.87%	87.26%
TOTAL LIABILITIES
Total Short-Term Liabilities	$563.7M	$849.2M	$763.3M
Total Long-Term Liabilities	$212.3M	$160.8M	$124.9M
Total Liabilities	$3.214B	$3.441B	$3.349B
YoY Change	-4.03%	-1.96%	1.31%
SHAREHOLDERS EQUITY
Retained Earnings	$1.227B	$1.679B	$1.623B
YoY Change	-24.37%	17.67%	17.52%
Common Stock	$1.635B	$1.631B	$1.625B
YoY Change	0.62%	0.16%	0.22%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$0.00	$18.20M	$18.20M
YoY Change	-100.0%	-40.52%	-40.52%
Treasury Stock Shares	1.705K shares	609.8K shares	609.8K shares
Shareholders Equity	$1.734B	$2.090B	$2.168B
YoY Change
Total Liabilities & Shareholders Equity	$5.064B	$5.635B	$5.629B
YoY Change	-10.04%	2.41%	4.45%

Cashflow Statement

Concept	2020 Q3	2019 Q4	2019 Q3
OPERATING ACTIVITIES
Net Income	-$50.10M	$56.50M	$111.0M
YoY Change	-145.14%	37.47%	119.8%
Depreciation, Depletion And Amortization	$35.40M	$36.50M	$37.00M
YoY Change	-4.32%	-7.12%	-3.65%
Cash From Operating Activities	$59.40M	$240.1M	$94.40M
YoY Change	-37.08%	-13.07%	15.69%
INVESTING ACTIVITIES
Capital Expenditures	-$28.60M	-$70.10M	-$46.90M
YoY Change	-39.02%	84.96%	52.77%
Acquisitions
YoY Change
Other Investing Activities	$1.200M	$2.400M	$184.9M
YoY Change	-99.35%	26.32%	-2250.0%
Cash From Investing Activities	-$27.40M	-$67.70M	$138.0M
YoY Change	-119.86%	88.06%	-451.15%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	1.100M	-192.9M	-2.300M
YoY Change	-147.83%	1548.72%	-79.46%
NET CHANGE
Cash From Operating Activities	59.40M	240.1M	94.40M
Cash From Investing Activities	-27.40M	-67.70M	138.0M
Cash From Financing Activities	1.100M	-192.9M	-2.300M
Net Change In Cash	33.10M	-20.50M	230.1M
YoY Change	-85.61%	-108.97%	639.87%
FREE CASH FLOW
Cash From Operating Activities	$59.40M	$240.1M	$94.40M
Capital Expenditures	-$28.60M	-$70.10M	-$46.90M
Free Cash Flow	$88.00M	$310.2M	$141.3M
YoY Change	-37.72%	-1.24%	25.82%

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	2020
	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	2020-09-30
	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
CY2020Q4	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	126816444	shares
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CY2020Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	388000000.0	USD
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CY2020Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	41700000	USD
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CY2020Q3	us-gaap	Inventory Net InventoryNet	1035900000	USD
CY2019Q4	us-gaap	Inventory Net InventoryNet	1155300000	USD
CY2020Q3	us-gaap	Other Assets Current OtherAssetsCurrent	48500000	USD
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CY2020Q3	us-gaap	Goodwill Goodwill	238400000	USD
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CY2020Q3	us-gaap	Minority Interest MinorityInterest	116100000	USD
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	us-gaap	Profit Loss ProfitLoss	210100000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	23200000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-16300000	USD
	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	14000000.0	USD
	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-13800000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	6100000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	14300000	USD
	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	-4200000	USD
	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	19100000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	-400000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	800000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	-6400000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	-600000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesTax	0	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesTax	0	USD
	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesTax	0	USD
	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesTax	0	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	6500000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	13500000	USD
	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	2200000	USD
	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	19700000	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
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-21900000	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
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-65400000	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
CY2019Q3	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	-700000	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
	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	-1900000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	0	USD
CY2019Q3	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	0	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	0	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-20500000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-21200000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-61600000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-63500000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	50200000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	18400000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	77800000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	69400000	USD
CY2020Q3	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	3200000	USD
CY2019Q3	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	133700000	USD
	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	-365500000	USD
	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	279500000	USD
CY2020Q3	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	9100000	USD
CY2019Q3	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	-300000	USD
	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	13000000.0	USD
	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	6000000.0	USD
CY2020Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-5900000	USD
CY2019Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	134000000.0	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-378500000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	273500000	USD
	us-gaap	Profit Loss ProfitLoss	-443300000	USD
	us-gaap	Profit Loss ProfitLoss	210100000	USD
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	108300000	USD
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	114600000	USD
	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	98500000	USD
	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	4100000	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000.0	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21500000	USD
	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	3300000	USD
	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	90600000	USD
	us-gaap	Disposal Group Not Discontinued Operation Gain Loss On Disposal DisposalGroupNotDiscontinuedOperationGainLossOnDisposal	0	USD
	us-gaap	Disposal Group Not Discontinued Operation Gain Loss On Disposal DisposalGroupNotDiscontinuedOperationGainLossOnDisposal	-1800000	USD
	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-119300000	USD
	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-12200000	USD
	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-166200000	USD
	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	92500000	USD
	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	-280500000	USD
	us-gaap	Increase Decrease In Accounts Payable Trade IncreaseDecreaseInAccountsPayableTrade	-75200000	USD
	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	-78300000	USD
	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	-86000000.0	USD
	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-49600000	USD
	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	8500000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	45000000.0	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	-10000000.0	USD
	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	94600000	USD
	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	98100000	USD
	us-gaap	Payments For Proceeds From Businesses And Interest In Affiliates PaymentsForProceedsFromBusinessesAndInterestInAffiliates	0	USD
	us-gaap	Payments For Proceeds From Businesses And Interest In Affiliates PaymentsForProceedsFromBusinessesAndInterestInAffiliates	-155900000	USD
	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	4000000.0	USD
	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	91800000	USD
	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-1400000	USD
	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	200000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-89200000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	149400000	USD
	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	391400000	USD
	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	0	USD
	us-gaap	Repayments Of Long Term Debt And Capital Securities RepaymentsOfLongTermDebtAndCapitalSecurities	209500000	USD
	us-gaap	Repayments Of Long Term Debt And Capital Securities RepaymentsOfLongTermDebtAndCapitalSecurities	5300000	USD
	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	-900000	USD
	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	5100000	USD
	ati	Payment Of Capped Call Transactions Cost PaymentOfCappedCallTransactionsCost	19400000	USD
	ati	Payment Of Capped Call Transactions Cost PaymentOfCappedCallTransactionsCost	0	USD
	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	9100000	USD
	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	0	USD
	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	19100000	USD
	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	0	USD
	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	7800000	USD
	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	9900000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	125600000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-10100000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	81400000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	129300000	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
CY2020Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	572200000	USD
CY2019Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	511300000	USD
CY2019Q2	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	2138600000	USD
CY2019Q3	us-gaap	Profit Loss ProfitLoss	115300000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	18400000	USD
CY2019Q3	ati	Employee Stock Plans EmployeeStockPlans	-7600000	USD
CY2019Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	2279900000	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
CY2018Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1991600000	USD
	us-gaap	Profit Loss ProfitLoss	210100000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	69400000	USD
	ati	Employee Stock Plans EmployeeStockPlans	-8800000	USD
CY2019Q3	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	2279900000	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
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2019Q4	ati	Entity Number Of Employees Covered By Usw Collective Bargaining Agreements Expiring February292020 EntityNumberOfEmployeesCoveredByUSWCollectiveBargainingAgreementsExpiringFebruary292020	1500	employee
	us-gaap	Description Of New Accounting Pronouncements Not Yet Adopted DescriptionOfNewAccountingPronouncementsNotYetAdopted	<div style="margin-top:9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%">Pending Accounting Pronouncements</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%">In August 2020, the FASB issued new accounting guidance related to accounting for convertible instruments. Under this new guidance, embedded conversion features are no longer separated from the host contract for convertible instruments with conversion features that are not required to be accounted for as derivatives, or that do not result in substantial premiums accounted for as paid-in capital. As such, a convertible debt instrument will be accounted for as a single liability measured at its amortized cost, as long as no other features require bifurcation and recognition as derivatives. By removing those separation models, the reported interest rate of convertible debt instruments typically will be closer to the coupon interest rate. The new guidance also addresses how convertible instruments are accounted for in the diluted earnings per share calculation, requiring the if-converted method, and requires enhanced disclosures about the terms of convertible instruments and contracts in an entity’s own equity. This new guidance is effective for the Company in fiscal year 2022, with early adoption permitted. </span></div>The Company expects to early adopt this new accounting guidance related to accounting for convertible instruments effective January 1, 2021 using the modified transition approach with the cumulative effect recognized as an adjustment to the opening balance of retained earnings. This new guidance is applicable to the Company’s 3.5% Convertible Senior Notes due 2025 (the 2025 Convertible Notes) that were issued in June 2020, for which the embedded conversion option was required to be separately accounted for as a component of stockholders’ equity. As such, upon adoption on January 1, 2021, the $49.8 million value of the embedded conversion, which is net of allocated offering costs, that was classified in additional paid-in-capital in stockholders’ equity will be reclassified to long-term debt on the consolidated balance sheet and will no longer be amortized as additional non-cash interest expense over the term of the 2025 Convertible Notes using the effective interest method, resulting in reported interest expense for the 2025 Convertible Notes that is closer to the 3.5% cash coupon rate. The $4.6 million of non-cash interest expense recorded in fiscal year 2020 for the amortization of the portion of the 2025 Convertible Notes that was allocated to stockholders’ equity will be shown as an adjustment to the opening balance of retained earnings on January 1, 2021 with an offset to long-term debt on the consolidated balance sheet. These expected effects of adoption exclude any effects related to deferred taxes. There will be no impact to the Company’s earnings per share calculation as it previously applied the if-converted method to the 2025 Convertible Notes given ATI’s flexibility to settle conversions of the 2025 Convertible Notes in cash, shares of ATI’s common stock or a combination thereof, at ATI’s election.
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2020Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	598000000.0	USD
CY2019Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1018700000	USD
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2323800000	USD
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3103900000	USD
CY2020Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	598000000.0	USD
CY2019Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1018700000	USD
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2323800000	USD
	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3103900000	USD
CY2020Q3	ati	Revenuefrom Contractwith Customer Excluding Assessed Tax Percentageof Revenue RevenuefromContractwithCustomerExcludingAssessedTaxPercentageofRevenue	1
CY2019Q3	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
CY2020Q3	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	1440000000	USD
CY2019Q3	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	2340000000	USD
CY2020Q3	ati	Revenue Remaining Performance Obligation Current RevenueRemainingPerformanceObligationCurrent	0.70	USD
CY2020Q3	ati	Accountsreceivablewithcustomers Accountsreceivablewithcustomers	392300000	USD
CY2019Q4	ati	Accountsreceivablewithcustomers Accountsreceivablewithcustomers	558700000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	4600000	USD
CY2018Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	6000000.0	USD
	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	100000	USD
	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	300000	USD
	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	400000	USD
	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	1300000	USD
CY2020Q3	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	4300000	USD
CY2019Q3	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	5000000.0	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
	ati	Contractwith Customer Asset Current Period Increase ContractwithCustomerAssetCurrentPeriodIncrease	55800000	USD
	ati	Contractwith Customer Asset Current Period Increase ContractwithCustomerAssetCurrentPeriodIncrease	57000000.0	USD
	ati	Contractwith Customer Asset Current Reclassifiedto Receivable ContractwithCustomerAssetCurrentReclassifiedtoReceivable	52700000	USD
	ati	Contractwith Customer Asset Current Reclassifiedto Receivable ContractwithCustomerAssetCurrentReclassifiedtoReceivable	63100000	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	-100000	USD
	ati	Contractwith Customer Asset Current Reclassification ContractwithCustomerAssetCurrentReclassification	0	USD
	ati	Contract With Customers Asset Current Divestiture ContractWithCustomersAssetCurrentDivestiture	0	USD
	ati	Contract With Customers Asset Current Divestiture ContractWithCustomersAssetCurrentDivestiture	7300000	USD
CY2020Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	41700000	USD
CY2019Q3	us-gaap	Contract With Customer Asset Net Current ContractWithCustomerAssetNetCurrent	37800000	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
	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	100000	USD
	ati	Contractwith Customer Asset Noncurrent Reclassification ContractwithCustomerAssetNoncurrentReclassification	0	USD
CY2020Q3	us-gaap	Contract With Customer Asset Net Noncurrent ContractWithCustomerAssetNetNoncurrent	0	USD
CY2019Q3	us-gaap	Contract With Customer Asset Net Noncurrent ContractWithCustomerAssetNetNoncurrent	100000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	78700000	USD
CY2018Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	71400000	USD
	ati	Contractwith Customer Liability Current Period Increase ContractwithCustomerLiabilityCurrentPeriodIncrease	121500000	USD
	ati	Contractwith Customer Liability Current Period Increase ContractwithCustomerLiabilityCurrentPeriodIncrease	104200000	USD
	ati	Contractwith Customer Liability Current Reclassifiedto Revenue ContractwithCustomerLiabilityCurrentReclassifiedtoRevenue	-42900000	USD
	ati	Contractwith Customer Liability Current Reclassifiedto Revenue ContractwithCustomerLiabilityCurrentReclassifiedtoRevenue	-43900000	USD
	ati	Contractwith Customer Liability Current Revenue Recognized ContractwithCustomerLiabilityCurrentRevenueRecognized	-65600000	USD
	ati	Contractwith Customer Liability Current Revenue Recognized ContractwithCustomerLiabilityCurrentRevenueRecognized	-34800000	USD
	ati	Contractwith Customer Liability Current Other ContractwithCustomerLiabilityCurrentOther	0	USD
	ati	Contractwith Customer Liability Current Other ContractwithCustomerLiabilityCurrentOther	200000	USD
	ati	Contractwith Customer Liability Current Reclassification ContractwithCustomerLiabilityCurrentReclassification	-6100000	USD
	ati	Contractwith Customer Liability Current Reclassification ContractwithCustomerLiabilityCurrentReclassification	0	USD
CY2020Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	97800000	USD
CY2019Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	97100000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	25900000	USD
CY2018Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	7300000	USD
	ati	Contractwith Customer Liability Noncurrent Period Increase ContractwithCustomerLiabilityNoncurrentPeriodIncrease	12900000	USD
	ati	Contractwith Customer Liability Noncurrent Period Increase ContractwithCustomerLiabilityNoncurrentPeriodIncrease	800000	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	6100000	USD
	ati	Contractwith Customer Liability Noncurrent Reclassification ContractwithCustomerLiabilityNoncurrentReclassification	0	USD
CY2020Q3	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	31900000	USD
CY2019Q3	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	7300000	USD
CY2020Q3	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	5600000	USD
CY2019Q4	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	6500000	USD
CY2019Q4	us-gaap	Inventory Lifo Reserve InventoryLIFOReserve	-33600000	USD
CY2020Q3	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	124700000	USD
CY2020Q3	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	400000	USD
	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1100000	USD
CY2019Q3	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	400000	USD
	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1000000.0	USD
CY2020Q3	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	210500000	USD
CY2019Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	164900000	USD
CY2020Q3	us-gaap	Inventory Work In Process InventoryWorkInProcess	717900000	USD
CY2019Q4	us-gaap	Inventory Work In Process InventoryWorkInProcess	899600000	USD
CY2020Q3	us-gaap	Inventory Finished Goods InventoryFinishedGoods	191100000	USD
CY2019Q4	us-gaap	Inventory Finished Goods InventoryFinishedGoods	161300000	USD
CY2020Q3	us-gaap	Inventory Gross InventoryGross	1119500000	USD
CY2019Q4	us-gaap	Inventory Gross InventoryGross	1225800000	USD
CY2020Q3	us-gaap	Inventory Lifo Reserve InventoryLIFOReserve	-41100000	USD
CY2019Q4	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	104100000	USD
CY2020Q3	us-gaap	Inventory Net InventoryNet	1035900000	USD
CY2019Q4	us-gaap	Inventory Net InventoryNet	1155300000	USD
	us-gaap	Inventory Lifo Reserve Period Charge InventoryLIFOReservePeriodCharge	-7500000	USD
	us-gaap	Inventory Lifo Reserve Period Charge InventoryLIFOReservePeriodCharge	1400000	USD
	ati	Inventory Net Realizable Value Reserve Period Charge InventoryNetRealizableValueReservePeriodCharge	7500000	USD
	ati	Inventory Net Realizable Value Reserve Period Charge InventoryNetRealizableValueReservePeriodCharge	-1300000	USD
	ati	Lifo Provision Benefitand Changein Debit Lifonr Vreservenet LifoProvisionBenefitandChangeinDebitLIFONRVreservenet	0	USD
	ati	Lifo Provision Benefitand Changein Debit Lifonr Vreservenet LifoProvisionBenefitandChangeinDebitLIFONRVreservenet	100000	USD
CY2020Q3	us-gaap	Land Land	35000000.0	USD
CY2019Q4	us-gaap	Land Land	34600000	USD
CY2020Q3	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	884200000	USD
CY2019Q4	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	832700000	USD
CY2020Q3	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	3721700000	USD
CY2019Q4	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	3671300000	USD
CY2020Q3	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	4640900000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	4538600000	USD
CY2020Q3	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	2174300000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	2088500000	USD
CY2020Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	2466600000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	2450100000	USD
CY2020Q3	us-gaap	Construction In Progress Gross ConstructionInProgressGross	223100000	USD
CY2020Q3	us-gaap	Goodwill Goodwill	238400000	USD
	us-gaap	Goodwill Period Increase Decrease GoodwillPeriodIncreaseDecrease	-287400000	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000.0	USD
	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	-400000	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000.0	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000.0	USD
CY2020Q3	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	528000000.0	USD
CY2019Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	241000000.0	USD
CY2020Q3	us-gaap	Goodwill Goodwill	238400000	USD
CY2020Q3	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	100000	USD
CY2019Q3	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	1400000	USD
	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	600000	USD
	ati	Rent Royalty And Other Income RentRoyaltyAndOtherIncome	2800000	USD
CY2020Q3	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	800000	USD
CY2019Q3	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	62300000	USD
	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	3300000	USD
	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	90600000	USD
CY2020Q3	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-1000000.0	USD
CY2019Q3	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-2400000	USD
	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-6600000	USD
	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-8700000	USD
CY2020Q3	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	0	USD
CY2019Q3	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	5800000	USD
	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	0	USD
	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	-1900000	USD
CY2020Q3	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	0	USD
CY2019Q3	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	0	USD
	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	4300000	USD
	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	0	USD
CY2020Q3	ati	Other Nonoperating Income Expense Other OtherNonoperatingIncomeExpenseOther	-300000	USD
CY2019Q3	ati	Other Nonoperating Income Expense Other OtherNonoperatingIncomeExpenseOther	100000	USD
	ati	Other Nonoperating Income Expense Other OtherNonoperatingIncomeExpenseOther	0	USD
	ati	Other Nonoperating Income Expense Other OtherNonoperatingIncomeExpenseOther	100000	USD
CY2020Q3	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-400000	USD
CY2019Q3	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	67200000	USD
	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-800000	USD
	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	82900000	USD
	us-gaap	Gain Loss On Sale Of Property GainLossOnSaleOfProperty	2500000	USD
CY2019Q3	us-gaap	Gain Loss On Sale Of Property GainLossOnSaleOfProperty	62400000	USD
	us-gaap	Gain Loss On Sale Of Property GainLossOnSaleOfProperty	91700000	USD
	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	4300000	USD
CY2020Q3	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	15200000	USD
CY2019Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	12300000	USD
CY2020Q3	ati	Total Debt TotalDebt	1541200000	USD
CY2019Q4	ati	Total Debt TotalDebt	1398900000	USD
CY2020Q3	us-gaap	Debt Current DebtCurrent	12200000	USD
CY2019Q4	us-gaap	Debt Current DebtCurrent	11500000	USD
CY2020Q3	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	1529000000.0	USD
CY2019Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	1387400000	USD
	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21500000	USD
	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	19100000	USD
	ati	Payment Of Capped Call Transactions Cost PaymentOfCappedCallTransactionsCost	19400000	USD
CY2020Q2	ati	Debt Instrument Convertible Redemption Price As A Percent Of Principal Amount DebtInstrumentConvertibleRedemptionPriceAsAPercentOfPrincipalAmount	1
CY2020Q2	us-gaap	Debt Instrument Convertible Threshold Percentage Of Stock Price Trigger DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger	1.30
CY2020Q2	us-gaap	Debt Instrument Convertible Threshold Trading Days DebtInstrumentConvertibleThresholdTradingDays	20	tradingDays
CY2020Q2	us-gaap	Debt Instrument Convertible Threshold Consecutive Trading Days1 DebtInstrumentConvertibleThresholdConsecutiveTradingDays1	30	tradingDays
CY2020Q2	ati	Debt Instrument Convertible Redemption Price As A Percent Of Principal Amount DebtInstrumentConvertibleRedemptionPriceAsAPercentOfPrincipalAmount	1
CY2020Q3	ati	Debt Instrument Convertible Cap Price DebtInstrumentConvertibleCapPrice	19.76
	ati	Percentage Of Raw Material Usage Hedged PercentageOfRawMaterialUsageHedged	0.05
	ati	Percentage Of Forecasted Natural Gas Usage Hedgedfor Year1 PercentageOfForecastedNaturalGasUsageHedgedforYear1	1
	ati	Percentage Of Forecasted Natural Gas Usage Hedgedfor Year2 PercentageOfForecastedNaturalGasUsageHedgedforYear2	0.70
	ati	Percentage Of Forecasted Natural Gas Usage Hedged For Year3 PercentageOfForecastedNaturalGasUsageHedgedForYear3	0.25
CY2020Q3	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	4100000	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	5600000	USD
CY2020Q3	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	4300000	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	7500000	USD
	us-gaap	Cash Flow Hedge Gain Loss To Be Reclassified Within Twelve Months CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths	1700000	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	99000000.0	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3700000	USD
CY2019Q3	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.031
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2020Q3	ati	Segment Operating Profit Loss SegmentOperatingProfitLoss	-6800000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10300000	USD
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.047
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2019Q3	ati	Segment Operating Profit Loss SegmentOperatingProfitLoss	99200000	USD
	ati	Segment Operating Profit Loss SegmentOperatingProfitLoss	101700000	USD
	ati	Segment Operating Profit Loss SegmentOperatingProfitLoss	275400000	USD
CY2020Q3	ati	Lifo Provision Benefitand Changein Debit Lifonr Vreservenet LifoProvisionBenefitandChangeinDebitLIFONRVreservenet	0	USD
CY2019Q3	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	100000	USD
CY2020Q3	ati	Corporate Expenses CorporateExpenses	10900000	USD
CY2019Q3	ati	Corporate Expenses CorporateExpenses	16000000.0	USD
	ati	Corporate Expenses CorporateExpenses	31400000	USD
	ati	Corporate Expenses CorporateExpenses	50600000	USD
CY2020Q3	ati	Other Income Expense OtherIncomeExpense	-1100000	USD
CY2019Q3	ati	Other Income Expense OtherIncomeExpense	-8200000	USD
	ati	Other Income Expense OtherIncomeExpense	-5300000	USD
	ati	Other Income Expense OtherIncomeExpense	-19200000	USD
CY2020Q3	ati	Restructuringandothercharges Restructuringandothercharges	2300000	USD
CY2019Q3	ati	Restructuringandothercharges Restructuringandothercharges	0	USD
	ati	Restructuringandothercharges Restructuringandothercharges	27000000.0	USD
	ati	Restructuringandothercharges Restructuringandothercharges	0	USD
CY2020Q3	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2019Q3	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	287000000.0	USD
	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2020Q3	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	0	USD
CY2019Q3	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	68200000	USD
	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	2500000	USD
	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	89800000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	111000000.0	USD
CY2020Q3	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2019Q3	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-21500000	USD
	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2020Q3	ati	Interest Expense Net InterestExpenseNet	25100000	USD
CY2019Q3	ati	Interest Expense Net InterestExpenseNet	24200000	USD
	ati	Interest Expense Net InterestExpenseNet	68700000	USD
	ati	Interest Expense Net InterestExpenseNet	74900000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-46200000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	119000000.0	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-339100000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	220400000	USD
	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	4300000	USD
	us-gaap	Gain Loss On Sale Of Property GainLossOnSaleOfProperty	2500000	USD
CY2019Q3	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	68200000	USD
CY2019Q3	us-gaap	Gain Loss On Sale Of Property GainLossOnSaleOfProperty	62400000	USD
	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	89800000	USD
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	126500000	shares
	us-gaap	Gain Loss On Sale Of Property GainLossOnSaleOfProperty	91700000	USD
CY2020Q3	us-gaap	Restructuring Charges RestructuringCharges	2300000	USD
	us-gaap	Restructuring Charges RestructuringCharges	27000000.0	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
CY2019Q4	us-gaap	Restructuring Reserve RestructuringReserve	4500000	USD
	us-gaap	Restructuring Charges RestructuringCharges	27000000.0	USD
	us-gaap	Payments For Restructuring PaymentsForRestructuring	11400000	USD
CY2020Q3	us-gaap	Restructuring Reserve RestructuringReserve	20100000	USD
CY2020Q3	us-gaap	Restructuring Reserve RestructuringReserve	20100000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	-50100000	USD
	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	-451600000	USD
	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	201100000	USD
CY2020Q3	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	-50100000	USD
CY2019Q3	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	114200000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	-451600000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	210800000	USD
CY2020Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	126600000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	125900000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	126500000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	125700000	shares
CY2020Q3	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	0	shares
CY2019Q3	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	900000	shares
	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	0	shares
	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	800000	shares
CY2020Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	126600000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	146700000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	146400000	shares
CY2020Q3	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	-0.40
CY2019Q3	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.88
	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	-3.57
	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	1.60
CY2020Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	-0.40
CY2019Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.78
	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	-3.57
	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.44
CY2020Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	25000000.0	shares
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	21900000	shares
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2019Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
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
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	4700000	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	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	6000000.0	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	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
CY2020Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	14500000	USD
CY2019Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1084400000	USD
CY2019Q2	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	12700000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-1100000	USD
CY2019Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-24100000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	23000000.0	USD
CY2019Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1061400000	USD
CY2019Q3	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	-4600000	USD
CY2019Q3	ati	Reclassificationfrom Accumulated Other Comprehensive Income Loss Current Period Netof Tax Attributableto Noncontrolling Interest ReclassificationfromAccumulatedOtherComprehensiveIncomeLossCurrentPeriodNetofTaxAttributabletoNoncontrollingInterest	0	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	-4600000	USD
CY2019Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	8100000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1133800000	USD
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	3500000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-68900000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	72400000	USD
CY2019Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-1061400000	USD
	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	89800000	USD
CY2018Q4	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	11100000	USD
	ati	Other Comprehensive Income Loss Before Reclassification Adjustments Net Of Tax Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossBeforeReclassificationAdjustmentsNetOfTaxAttributableToNoncontrollingInterest	-3000000.0	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	-3000000.0	USD
CY2019Q3	ati	Accumulated Other Comprehensive Income Loss Netof Tax Attributableto Noncontrolling Interest AccumulatedOtherComprehensiveIncomeLossNetofTaxAttributabletoNoncontrollingInterest	8100000	USD
CY2020Q3	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	14000000	USD
CY2020Q3	us-gaap	Accrued Environmental Loss Contingencies Current AccruedEnvironmentalLossContingenciesCurrent	4000000	USD
CY2020Q3	ati	Environmental Remediation Obligation Federal Superfund Sites EnvironmentalRemediationObligationFederalSuperfundSites	3000000	USD
CY2020Q3	ati	Environmental Remediation Obligation For Formerly Owned Sites EnvironmentalRemediationObligationForFormerlyOwnedSites	9000000	USD
CY2020Q3	ati	Environmental Remediation Obligation For Owned Or Controlled Sites With Closed Operations EnvironmentalRemediationObligationForOwnedOrControlledSitesWithClosedOperations	1000000	USD
CY2020Q3	ati	Environmental Remediation Obligation For Ongoing Operations EnvironmentalRemediationObligationForOngoingOperations	1000000	USD
CY2019Q3	us-gaap	Gain Loss On Sales Of Assets And Asset Impairment Charges GainLossOnSalesOfAssetsAndAssetImpairmentCharges	68200000	USD
CY2019Q3	us-gaap	Gain Loss On Sale Of Property GainLossOnSaleOfProperty	62400000	USD
	us-gaap	Gain Loss On Sale Of Property GainLossOnSaleOfProperty	91700000	USD
CY2020Q2	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	99000000.0	USD

Files In Submission

Name	View Source	Status
0001628280-20-015070-index-headers.html	Edgar Link	pending
0001628280-20-015070-index.html	Edgar Link	pending
0001628280-20-015070.txt	Edgar Link	pending
0001628280-20-015070-xbrl.zip	Edgar Link	pending
ati-20200930.htm	Edgar Link	pending
ati-20200930.xsd	Edgar Link	pending
ati-20200930_cal.xml	Edgar Link	unprocessable
ati-20200930_def.xml	Edgar Link	unprocessable
ati-20200930_htm.xml	Edgar Link	completed
ati-20200930_lab.xml	Edgar Link	unprocessable
ati-20200930_pre.xml	Edgar Link	unprocessable
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
fy2020q3exhibit311.htm	Edgar Link	pending
fy2020q3exhibit312.htm	Edgar Link	pending
fy2020q3exhibit321.htm	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
R1.htm	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

2020 Q3 Form 10-Q Financial Statement

#000162828020015070 Filed on October 29, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ATI ATI INC Stock $ati

2020 Q3 Form 10-Q Financial Statement

#000162828020015070 Filed on October 29, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ATI
ATI INC Stock $ati