Document and Entity Information - shares	3 Months Ended
	Sep. 30, 2016	Oct. 28, 2016
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q1
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		33,063,243