Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Nov. 30, 2020	Mar. 31, 2020
Cover [Abstract]
Entity Registrant Name	INNOVATIVE SOLUTIONS & SUPPORT INC
Entity Central Index Key	0000836690
Document Type	10-K
Document Period End Date	Sep. 30, 2020
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 41.4
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		17,214,384
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock par value $.001 per share
Security Exchange Name	NASDAQ
Trading Symbol	ISSC