Segment Reporting - Company's Revenue by Geographic Region (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015
Revenue from External Customer [Line Items]
Total revenue	$ 100,490	$ 93,200	$ 222,789	$ 248,406
Hong Kong [Member]
Revenue from External Customer [Line Items]
Total revenue	92,588	84,053	197,478	228,371
Europe [Member]
Revenue from External Customer [Line Items]
Total revenue	2,228	2,260	10,862	5,963
United States [Member]
Revenue from External Customer [Line Items]
Total revenue	1,523	2,190	5,697	4,756
Asia Pacific [Member]
Revenue from External Customer [Line Items]
Total revenue	2,889	1,015	6,125	2,331
North America other than United States [Member]
Revenue from External Customer [Line Items]
Total revenue	$ 1,262	$ 3,682	$ 2,627	$ 6,985