Segment Reporting - Company's Revenue by Geographic Region Based on Bill-to Location (Detail) - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2017	Apr. 30, 2016
Revenue from External Customer [Line Items]
Total revenue	$ 64,135	$ 57,157
Taiwan [Member]
Revenue from External Customer [Line Items]
Total revenue	46,416	42,102
Asia Pacific [Member]
Revenue from External Customer [Line Items]
Total revenue	11,759	7,586
United States [Member]
Revenue from External Customer [Line Items]
Total revenue	2,055	1,847
North America other than United States [Member]
Revenue from External Customer [Line Items]
Total revenue	2,005	270
Europe [Member]
Revenue from External Customer [Line Items]
Total revenue	$ 1,900	$ 5,352