Financial Instruments and Fair Value - Schedule of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Jan. 31, 2017	Jan. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable securities	$ 100,850	$ 40,367
Included in cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable securities	18,328	530
Included in marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable securities	$ 82,522	$ 39,837