Financial Instruments and Fair Value - Schedule of Available-for-Sale Securities at Fair Value (Detail) - USD ($) $ in Thousands	Oct. 31, 2015	Jan. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 40,311	$ 40,131
Unrealized Gains	6	9
Unrealized Losses	(21)	(10)
Fair Value	40,296	40,130
Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	41	2,427
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	41	2,427
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,145	1,497
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	2,145	1,497
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	28,549	32,356
Unrealized Gains	6	9
Unrealized Losses	(17)	(10)
Fair Value	28,538	32,355
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,596	3,851
Unrealized Gains	0	0
Unrealized Losses	(1)	0
Fair Value	4,595	$ 3,851
U.S. government securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,911
Unrealized Gains	0
Unrealized Losses	(3)
Fair Value	2,908
Agency bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,069
Unrealized Gains	0
Unrealized Losses	0
Fair Value	$ 2,069

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

+ References

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This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
-Paragraph 1
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Amount of debt securities categorized neither as held-to-maturity nor trading.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
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-Name Accounting Standards Codification
-Topic 320
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-Section 45
-Paragraph 1
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

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