Document and Entity Information - USD ($)	12 Months Ended
	Jun. 30, 2017	Aug. 08, 2017	Dec. 31, 2016
Document and Entity Information
Entity Registrant Name	CARPENTER TECHNOLOGY CORP
Entity Central Index Key	0000017843
Current Fiscal Year End Date	--06-30
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		46,757,548
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 1,689,766,058