Segment Reporting - Company's Revenue by Geographic Region Based on Bill-to Location (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Revenue from External Customer [Line Items]
Total revenue	$ 57,286	$ 89,062	$ 176,698	$ 224,827
Taiwan [Member]
Revenue from External Customer [Line Items]
Total revenue	28,300	45,026	100,650	139,494
Asia Pacific [Member]
Revenue from External Customer [Line Items]
Total revenue	20,971	19,000	55,372	43,050
Europe [Member]
Revenue from External Customer [Line Items]
Total revenue	5,734	20,908	13,191	29,252
North America other than United States [Member]
Revenue from External Customer [Line Items]
Total revenue	1,531	2,582	5,040	7,566
United States [Member]
Revenue from External Customer [Line Items]
Total revenue	$ 750	$ 1,546	$ 2,445	$ 5,465