Segment Reporting - Company's Revenue by Geographic Region Based on Bill-to Location (Detail) - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Revenue from External Customer [Line Items]
Total revenue	$ 56,938	$ 64,135
Taiwan [Member]
Revenue from External Customer [Line Items]
Total revenue	33,206	46,416
Asia Pacific [Member]
Revenue from External Customer [Line Items]
Total revenue	16,356	11,759
Europe [Member]
Revenue from External Customer [Line Items]
Total revenue	4,582	1,900
North America other than United States [Member]
Revenue from External Customer [Line Items]
Total revenue	2,006	2,005
United States [Member]
Revenue from External Customer [Line Items]
Total revenue	$ 788	$ 2,055