Document And Entity Information - USD ($)	12 Months Ended
	Jun. 30, 2021	Sep. 10, 2021	Dec. 31, 2020
Document And Entity Information
Document Type	10-K/A
Amendment Flag	true
Amendment Description	Napco Security Technologies, Inc. ( “Company”) is filing this Amendment No. 1 on Form 10-K/A (the “Amendment”) to amend its Annual Report on Form 10-K for the fiscal year ended June 30, 2021, originally filed with the U.S. Securities and Exchange Commission (the “SEC”) on September 13, 2021 (the “Original Report”). In filing this amendment, the Company is restating its previously issued audited financial statements for the periods contained therein to account changes to the Company’s inventory obsolescence reserve. Those previously issued financial statements should no longer be relied upon. Except as described below, all other information in, and the exhibits to, the Original Report remain unchanged. Accordingly, this Amendment should be read in conjunction with the Original Report and with our filings with the SEC made after the Original Report. This Amendment speaks as of the date of the Original Report and the Company has not updated the Original Report to reflect events occurring subsequent to the date of the Original Report.
Document Annual Report	true
Document Period End Date	Jun. 30, 2021
Entity File Number	1-10004
Entity Registrant Name	NAPCO SECURITY TECHNOLOGIES, INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	11-2277818
Entity Address, Address Line One	333 Bayview Avenue
Entity Address, City or Town	Amityville
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	11701
City Area Code	631
Local Phone Number	842-9400
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	NSSC
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0000069633
Current Fiscal Year End Date	--06-30
ICFR Auditor Attestation Flag	false
Entity Public Float			$ 376,476,776
Entity Common Stock, Shares Outstanding		36,702,168