Segment Reporting - Company's Revenue by Geographic Region Based on Bill-to Location (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Revenue from External Customer [Line Items]
Total revenue	$ 50,113	$ 56,410	$ 104,758	$ 103,598
Taiwan [Member]
Revenue from External Customer [Line Items]
Total revenue	27,313	30,981	61,773	58,581
Asia Pacific [Member]
Revenue from External Customer [Line Items]
Total revenue	14,965	17,246	28,993	31,734
Europe [Member]
Revenue from External Customer [Line Items]
Total revenue	2,633	4,101	4,886	7,584
North America other than United States [Member]
Revenue from External Customer [Line Items]
Total revenue	3,343	3,001	6,016	3,884
United States [Member]
Revenue from External Customer [Line Items]
Total revenue	$ 1,859	$ 1,081	$ 3,090	$ 1,815