401(k) Plan (Details) - USD ($)	3 Months Ended		9 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Napco Technologies 401 k Plan [Member]
Schedule of Deferred Compensation Plans [Line Items]
Deferred compensation plan expense	$ 33,000	$ 34,000	$ 98,000	$ 99,000