NET INCOME (LOSS) PER SHARE - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017
Common Class A [Member]
Numerator:
Net income allocated, basic	$ 7,174	$ 4,548	$ 9,452	$ 7,664
Conversion of Class B to Class A shares	2,065	1,327	2,721	2,239
Effect of share-based compensation on allocated net income	0	6	0	8
Net income allocated, diluted	$ 9,239	$ 5,881	$ 12,173	$ 9,911
Denominator:
Weighted average shares outstanding, basic (in shares)	9,714	9,613	9,718	9,603
Conversion of Class B to Class A shares (in shares)	4,304	4,319	4,304	4,319
Dilutive effect of share-based compensation (in shares)	0	52	0	50
Weighted average shares outstanding, diluted (in shares)	14,018	13,984	14,022	13,972
Common Class B [Member]
Numerator:
Net income allocated, basic	$ 2,065	$ 1,327	$ 2,721	$ 2,239
Conversion of Class B to Class A shares	0	0	0	0
Effect of share-based compensation on allocated net income	0	(3)	0	(3)
Net income allocated, diluted	$ 2,065	$ 1,324	$ 2,721	$ 2,236
Denominator:
Weighted average shares outstanding, basic (in shares)	4,304	4,319	4,304	4,319
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	4,319	4,304	4,319