Financial Instruments and Fair Value - Summary of Contractual Maturities of Investments (Detail) - USD ($) $ in Thousands	Oct. 31, 2015	Jan. 31, 2015
Available For Sale Securities Debt Maturities Fair Value [Abstract]
Due within one year	$ 30,540	$ 37,559
Due within one to two years	9,756	2,571
Total cash equivalents and marketable securities	$ 40,296	$ 40,130