Share-Based Compensation, Nonvested Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jul. 28, 2017	Jul. 29, 2016	Jul. 31, 2015
Nonvested Stock Awards [Member]
Nonvested stock, shares [Roll Forward]
Unvested, beginning of period (in shares)	40,437
Granted (in shares)	94,432
Vested (in shares)	(102,852)
Forfeited (in shares)	0
Unvested, end of period (in shares)	32,017	40,437
Nonvested stock, weighted-average grant date fair value [Roll Forward]
Unvested, beginning of period (in dollars per share)	$ 112.52
Granted (in dollars per share)	154.63
Vested (in dollars per share)	142.93
Forfeited (in dollars per share)	0
Unvested, end of period (in dollars per share)	$ 139.04	$ 112.52
Total fair value of nonvested stock	$ 14,700	$ 8,418	$ 8,152
Nonvested Stock Awards [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Nonvested Stock Awards [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	5 years
2017 LTPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested stock earned (in shares)	13,704
2017 LTPP [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period	2017
Vesting period	2 years
2017 LTPP [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period	2018
Vesting period	3 years
2016 LTPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested stock earned (in shares)	28,797
2016 LTPP [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period	2016
Vesting period	2 years
2016 LTPP [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period	2017
Vesting period	3 years
Omnibus Plan 2010 [Member] | Nonvested Stock Units [Member]
Nonvested stock, weighted-average grant date fair value [Roll Forward]
Award performance period	3 years
Measurement period for average stock prices in consecutive calendar days	60 days
Measurement period for average stock prices prior to first business day of performance period	30 days
Measurement period for average stock prices after first business day of performance period	30 days
Risk-free interest rate for nonvested stock units granted minimum	1.00%
Risk-free interest rate for nonvested stock units granted maximum	1.40%
Nonvested stock units accrued (in shares)	3,025
Omnibus Plan 2010 [Member] | Nonvested Stock Units [Member] | Minimum [Member]
Nonvested stock, weighted-average grant date fair value [Roll Forward]
Percentage of shares of target award that may be awarded	75.00%
Omnibus Plan 2010 [Member] | Nonvested Stock Units [Member] | Maximum [Member]
Nonvested stock, weighted-average grant date fair value [Roll Forward]
Percentage of shares of target award that may be awarded	125.00%