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	0 Months Ended
	Jan. 31, 2015	Jan. 31, 2014
Asset backed-securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 9,319
Gross Unrealized Losses	(4)
Corporate notes and bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	23,239	1,403
Gross Unrealized Losses	(19)	(1)
U.S. agency obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	18,398
Gross Unrealized Losses	$ (3)