Stockholders' Equity (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
	Oct. 23, 2020	Oct. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Jan. 31, 2020	Jul. 22, 2019
Equity [Abstract]
Common stock, shares authorized (in shares)		500,000,000			500,000,000	500,000,000
Common stock, par value per share (in dollars per share)		$ 0.01			$ 0.01	$ 0.01
Issuance of common stock in public offering, net of issuance costs (in shares)	5,750,000
Issue price per share (in dollars per share)	$ 32.00
Issuance of common stock in public offering, net of issuance costs	$ 174,800	$ 174,510		$ 124,698
Issuance of common stock, issuance costs	$ 290	$ 290	$ 56	$ 6,084
Preferred stock, shares authorized (in shares)						20,000,000
Preferred stock, par value (in dollars per share)						$ 0.01
Preferred stock, shares issued (in shares)		0			0
Preferred stock, shares outstanding (in shares)		0			0