Divestiture (Details) - USD ($) $ in Millions	3 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Proceeds from divestiture of businesses	$ 17.6	$ 0.0
Discontinued Operations, Disposed of by Sale \| Amega West
Business Acquisition [Line Items]
Disposal group, including discontinued operation, consideration	20.0
Proceeds from divestiture of businesses	17.6
Disposal group, including discontinued operation, consideration, escrow	$ 2.4

Disposal Group, Including Discontinued Operation, Consideration, Escrow

No definition available.

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Namespace Prefix:	crs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

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- Definition

Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3179-108585

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- Details

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