Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Mar. 31, 2018	May 02, 2018	Sep. 29, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	CA, INC.
Entity Central Index Key	0000356028
Document Type	10-K
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--03-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 10.3
Entity Common Stock, Shares Outstanding		416,617,226