Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions				2 Months Ended	3 Months Ended
	Aug. 06, 2020	Jun. 16, 2020	May 08, 2020	Aug. 06, 2020	Sep. 10, 2020	Jul. 31, 2020	Jan. 31, 2020	Jul. 31, 2019	Aug. 24, 2020
2018 Omnibus Incentive Plan [Member]
Subsequent Event [Line Items]
Sale of common stock, net of fees (in shares)			4,333,333
Subsequent Event [Member] | 2018 Omnibus Incentive Plan [Member]
Subsequent Event [Line Items]
Common Stock, Reserved for Future Issuance									1,503,068
Common Stock [Member]
Subsequent Event [Line Items]
Sale of common stock, net of fees (in shares)						25,144,704	7,938,228	43,997,807
Common Stock [Member] | At Market Issuance Sales Agreement [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Sale of common stock, net of fees (in shares)	3,200,000			28,300,000	72,300,000
Average Sale of Stock Price Per Share	$ 2.51			$ 2.55
Gross Proceeds From Issuance Of Common Stock	$ 8.0			$ 72.3
Payments of Stock Issuance Costs	0.2			2.2
Proceeds from Issuance of Common Stock	$ 7.8			$ 70.1
Common Stock, Reserved for Future Issuance					2,700,000
Maximum [Member] | Common Stock [Member] | At Market Issuance Sales Agreement [Member]
Subsequent Event [Line Items]
Aggregate Offering Price		$ 75.0