Short-Term Investments - Schedule of Fair Values and Gross Unrealized Losses of Available-for-Sale Securities Aggregated by Investment Category (Detail) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2014	Jan. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Gross Unrealized Losses	$ (91)	$ (1)
Asset backed-securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value	2,293
Gross Unrealized Losses	(6)
Corporate notes and bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value	18,040	1,403
Gross Unrealized Losses	(21)	(1)
U.S. agency obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value	89,105
Gross Unrealized Losses	(52)
U.S. treasury securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value	15,688
Gross Unrealized Losses	$ (12)