Organization and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018	Feb. 01, 2019	Jan. 31, 2019
Summary Of Significant Accounting Policies [Line Items]
Material inventory losses recognized	$ 0	$ 0	$ 0	$ 0
Right-of-use assets	7,237,000		7,237,000			$ 0
Lease liabilities	7,360,000		7,360,000
Prepaid Expenses and Other Current Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Grants recorded	1,200,000		1,200,000
Other Non-current Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Grants recorded	$ 2,800,000		$ 2,800,000
ASU 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Right-of-use assets					$ 8,581,000
Lease liabilities					$ 8,700,000