Segment Reporting - Company's Revenue by Geographic Region (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Revenue from External Customer [Line Items]
Total revenue	$ 316,373	$ 218,278	$ 157,608
Hong Kong [Member]
Revenue from External Customer [Line Items]
Total revenue	284,722	196,372	135,382
Asia Pacific [Member]
Revenue from External Customer [Line Items]
Total revenue	3,930	2,358	2,809
United States [Member]
Revenue from External Customer [Line Items]
Total revenue	8,855	6,677	7,128
North America other than Unites States [Member]
Revenue from External Customer [Line Items]
Total revenue	9,953	6,076	4,594
Europe [Member]
Revenue from External Customer [Line Items]
Total revenue	$ 8,913	$ 6,795	$ 7,695