XML 110 R111.htm IDEA: XBRL DOCUMENT
v3.20.1

Business Segments (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Sales | $ 1,018.6 | $ 1,018.7 | $ 1,080.4 | $ 1,004.8 | $ 1,037.9 | $ 1,020.2 | $ 1,009.5 | $ 979.0 | $ 4,122.5 | $ 4,046.6 | $ 3,525.1
Operating Segments |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Sales |  |  |  |  |  |  |  |  | 4,446.4 | 4,341.6 | 3,758.0
Operating Segments | Intersegment Sales [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Sales |  |  |  |  |  |  |  |  | 323.9 | 295.0 | 232.9
Operating Segments | External Sales [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Sales |  |  |  |  |  |  |  |  | 4,122.5 | 4,046.6 | 3,525.1
Operating Segments | High Performance Materials & Components |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Sales |  |  |  |  |  |  |  |  | 2,054.2 | 2,039.2 | 1,751.1
Operating Segments | High Performance Materials & Components | Intersegment Sales [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Sales |  |  |  |  |  |  |  |  | 75.7 | 76.1 | 46.3
Operating Segments | High Performance Materials & Components | External Sales [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Sales |  |  |  |  |  |  |  |  | 1,978.5 | 1,963.1 | 1,704.8
Operating Segments | Advanced Alloys & Solutions |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Sales |  |  |  |  |  |  |  |  | 2,392.2 | 2,302.4 | 2,006.9
Operating Segments | Advanced Alloys & Solutions | Intersegment Sales [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Sales |  |  |  |  |  |  |  |  | 248.2 | 218.9 | 186.6
Operating Segments | Advanced Alloys & Solutions | External Sales [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Sales |  |  |  |  |  |  |  |  | $ 2,144.0 | $ 2,083.5 | $ 1,820.3

X
- Definition Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045 + Details
Name: | us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=ati_InternalCustomersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=ati_ExternalCustomersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=ati_HighPerformanceMaterialsComponentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=ati_AdvancedAlloysSolutionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |