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
	Oct. 31, 2014	Jan. 31, 2014	Oct. 31, 2014
Asset backed-securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value			$ 6,754
Gross Unrealized Losses	(2)
Corporate notes and bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value		1,403	33,490
Gross Unrealized Losses	(28)	(1)
U.S. agency obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value			34,215
Gross Unrealized Losses	$ (6)