Document and Entity Information - shares	3 Months Ended
	Dec. 31, 2020	Jan. 29, 2021
Cover [Abstract]
Entity Registrant Name	INNOVATIVE SOLUTIONS & SUPPORT INC
Entity Central Index Key	0000836690
Document Type	10-Q
Document Period End Date	Dec. 31, 2020
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		17,241,872
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false
Trading Symbol	ISSC