Document And Entity Information	3 Months Ended
	Dec. 31, 2012	Feb. 11, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	CSP INC /MA/
Document Type	10-Q
Current Fiscal Year End Date	--09-30
Entity Common Stock, Shares Outstanding		3,442,842
Amendment Flag	false
Entity Central Index Key	0000356037
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Smaller Reporting Company
Entity Well-known Seasoned Issuer	No
Document Period End Date	Dec. 31, 2012
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q1