Document and Entity Information - shares	9 Months Ended
	Mar. 31, 2017	Apr. 28, 2017
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Trading Symbol	CSII
Entity Registrant Name	CARDIOVASCULAR SYSTEMS INC
Entity Central Index Key	0001180145
Current Fiscal Year End Date	--06-30
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		32,712,058