XML 115 R101.htm IDEA: XBRL DOCUMENT
v3.22.4

Retirement Benefits (Details 14) $ in Millions | Dec. 31, 2022 USD ($)
--- | ---
Pension Benefits [Member] |
Defined Benefit Plan Expected Future Benefit Payments [Abstract] |
2023 | $ 157.5
2024 | 155.0
2025 | 152.3
2026 | 149.6
2027 | 146.8
2028-2032 | 684.0
Other Postretirement Benefits |
Defined Benefit Plan Expected Future Benefit Payments [Abstract] |
2023 | 27.8
2024 | 26.0
2025 | 24.0
2026 | 22.1
2027 | 20.4
2028-2032 | 77.5
Medicare Part D Subsidy [Abstract] |
2023 | 0.0
2024 | 0.0
2025 | 0.0
2026 | 0.0
2027 | 0.0
2028-2032 | $ 0.0

X
- Definition Defined Benefit Plan Expected Future Benefit Payments [Abstract] + References No definition available. + Details
Name: | ati_DefinedBenefitPlanExpectedFutureBenefitPaymentsAbstract
Namespace Prefix: | ati_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of benefit for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of benefit for defined benefit plan expected to be paid in next fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of benefit for defined benefit plan expected to be paid in fifth fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of benefit for defined benefit plan expected to be paid in fourth fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of benefit for defined benefit plan expected to be paid in third fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of benefit for defined benefit plan expected to be paid in second fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_DisclosureOfExpectedGrossPrescriptionDrugSubsidyReceiptsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of prescription drug subsidy receipt expected after fifth fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 + Details
Name: | us-gaap_PrescriptionDrugSubsidyReceiptsAfterYearFive
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of prescription drug subsidy receipt expected in next fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_PrescriptionDrugSubsidyReceiptsNextTwelveMonths
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of prescription drug subsidy receipt expected in fifth fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_PrescriptionDrugSubsidyReceiptsYearFive1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of prescription drug subsidy receipt expected in fourth fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_PrescriptionDrugSubsidyReceiptsYearFour1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of prescription drug subsidy receipt expected in third fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 + Details
Name: | us-gaap_PrescriptionDrugSubsidyReceiptsYearThree1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of prescription drug subsidy receipt expected in second fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_PrescriptionDrugSubsidyReceiptsYearTwo1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |