401(k) Plan (Details) - USD ($)	3 Months Ended		6 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Napco Technologies 401 k Plan
Schedule of Deferred Compensation Plans [Line Items]
Deferred compensation plan expense	$ 36,000	$ 34,000	$ 68,000	$ 64,000