| Cover | Dec. 10, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Dec. 10, 2020 |
| Entity File Number | 0-10004 |
| Entity Registrant Name | NAPCO SECURITY TECHNOLOGIES, INC. |
| Entity Central Index Key | 0000069633 |
| Entity Tax Identification Number | 11-2277818 |
| Entity Incorporation, State or Country Code | DE |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | NSSC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
