Financial Instruments and Fair Value - Summary of Contractual Maturities of Investments (Detail) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2015	Jan. 31, 2015
Available For Sale Securities Debt Maturities Fair Value [Abstract]
Due within one year	$ 33,672	$ 37,559
Due within one to two years	6,498	2,571
Total cash equivalents and marketable securities	$ 40,170	$ 40,130

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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