Financial Instruments and Fair Value - Schedule of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Jul. 31, 2017	Jan. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable securities	$ 101,309	$ 100,850
Included in cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable securities	10,232	18,328
Included in marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable securities	$ 91,077	$ 82,522