SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Jul. 28, 2018	Jul. 29, 2017
Class A Common Stock
Numerator:
Net income allocated, basic	$ 18,925	$ 17,354
Conversion of Class B to Class A shares	5,447	5,025
Effect of share-based compensation on allocated net income	0	25
Net income allocated, diluted	$ 24,372	$ 22,404
Denominator:
Weighted average shares outstanding, basic (in shares)	9,717	9,663
Conversion of Class B to Class A shares (in shares)	4,304	4,314
Dilutive effect of share-based compensation (in shares)	0	27
Weighted average shares outstanding, diluted (in shares)	14,021	14,004
Net income per share
Basic (in dollars per share)	$ 1.95	$ 1.80
Diluted (in dollars per share)	$ 1.74	$ 1.60
Class B Common Stock
Numerator:
Net income allocated, basic	$ 5,447	$ 5,025
Conversion of Class B to Class A shares	0	0
Effect of share-based compensation on allocated net income	0	(4)
Net income allocated, diluted	$ 5,447	$ 5,021
Denominator:
Weighted average shares outstanding, basic (in shares)	4,304	4,314
Conversion of Class B to Class A shares (in shares)	0	0
Dilutive effect of share-based compensation (in shares)	0	0
Weighted average shares outstanding, diluted (in shares)	4,304	4,314
Net income per share
Basic (in dollars per share)	$ 1.27	$ 1.16
Diluted (in dollars per share)	$ 1.27	$ 1.16