Financial Instruments and Fair Value - Schedule of Available-for-Sale Securities at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2015	Jan. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 40,187	$ 40,131
Unrealized Gains	2	9
Unrealized Losses	(19)	(10)
Fair Value	40,170	40,130
Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,236	2,427
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	1,236	2,427
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,499	1,497
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	1,499	1,497
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32,560	32,356
Unrealized Gains	2	9
Unrealized Losses	(18)	(10)
Fair Value	32,544	32,355
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,889	3,851
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	2,889	3,851
U.S. government securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	999
Unrealized Gains	0
Unrealized Losses	0
Fair Value	999
Agency bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,004
Unrealized Gains	0
Unrealized Losses	(1)
Fair Value	$ 1,003

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount of debt securities categorized neither as held-to-maturity nor trading.

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