Document and Entity Information (USD $)	12 Months Ended
	Jun. 30, 2012	Aug. 27, 2012	Dec. 31, 2011
Document and Entity Information [Abstract]
Entity Registrant Name	Cardiovascular Systems Inc
Entity Central Index Key	0001180145
Document Type	10-K
Document Period End Date	Jun. 30, 2012
Amendment Flag	false
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--06-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Public Float			$ 147,598,517
Entity Common Stock, Shares Outstanding		20,566,881