Fair Value Measurements - Schedule of Key Assumptions Used for Valuation of Preferred Stock Warrant Liability (Details) - $ / shares	3 Months Ended
	Oct. 28, 2017	Oct. 29, 2016
Financial Liabilities Fair Value Disclosure [Abstract]
Expected term (in years)	2 years	5 years 3 months 18 days
Fair value of underlying shares	$ 16.53	$ 8.89
Volatility	39.20%	40.20%
Risk free interest rate	1.60%	1.40%