401(k) Plan (Narrative) (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Napco Technologies 401 k Plan [Member]
Schedule of Deferred Compensation Plans [Line Items]
Deferred compensation plan expense	$ 26,000	$ 27,000	$ 81,000	$ 93,000