SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Jul. 27, 2019	Jul. 28, 2018
Class A Common Stock
Numerator:
Net income allocated, basic	$ 19,341	$ 18,925
Conversion of Class B to Class A shares	5,538	5,447
Effect of share-based compensation on allocated net income	0	0
Net income allocated, diluted	$ 24,879	$ 24,372
Denominator:
Weighted average shares outstanding, basic (in shares)	9,747	9,717
Conversion of Class B to Class A shares (in shares)	4,296	4,304
Dilutive effect of share-based compensation (in shares)	0	0
Weighted average shares outstanding, diluted (in shares)	14,043	14,021
Net income per share
Basic (in dollars per share)	$ 1.98	$ 1.95
Diluted (in dollars per share)	$ 1.77	$ 1.74
Class B Common Stock
Numerator:
Net income allocated, basic	$ 5,538	$ 5,447
Conversion of Class B to Class A shares	0	0
Effect of share-based compensation on allocated net income	(1)	0
Net income allocated, diluted	$ 5,537	$ 5,447
Denominator:
Weighted average shares outstanding, basic (in shares)	4,296	4,304
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)	4,296	4,304
Net income per share
Basic (in dollars per share)	$ 1.29	$ 1.27
Diluted (in dollars per share)	$ 1.29	$ 1.27