NET INCOME (LOSS) PER SHARE - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 28, 2018	Apr. 29, 2017	Apr. 28, 2018	Apr. 29, 2017
Common Class A [Member]
Numerator:
Net income allocated, basic	$ 4,935	$ 4,550	$ 14,387	$ 12,214
Conversion of Class B to Class A shares	1,421	1,312	4,142	3,551
Effect of share-based compensation on allocated net income	0	0	0	15
Net income allocated, diluted	$ 6,356	$ 5,862	$ 18,529	$ 15,780
Denominator:
Weighted average shares outstanding, basic (in shares)	9,709	9,696	9,715	9,634
Conversion of Class B to Class A shares (in shares)	4,304	4,316	4,304	4,318
Dilutive effect of share-based compensation (in shares)	0	0	0	36
Weighted average shares outstanding, diluted (in shares)	14,013	14,012	14,019	13,988
Common Class B [Member]
Numerator:
Net income allocated, basic	$ 1,421	$ 1,312	$ 4,142	$ 3,551
Conversion of Class B to Class A shares	0	0	0	0
Effect of share-based compensation on allocated net income	0	0	0	(4)
Net income allocated, diluted	$ 1,421	$ 1,312	$ 4,142	$ 3,547
Denominator:
Weighted average shares outstanding, basic (in shares)	4,304	4,316	4,304	4,318
Conversion of Class B to Class A shares (in shares)	0	0	0	0
Dilutive effect of share-based compensation (in shares)	0	0	0	0
Weighted average shares outstanding, diluted (in shares)	4,304	4,316	4,304	4,318