Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Summary of Available-for-Sale Securities (Detail)

v3.5.0.2
Fair Value Measurements - Summary of Available-for-Sale Securities (Detail) - USD ($)
$ in Thousands
Jul. 31, 2016
Jan. 31, 2016
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost $ 50,648 $ 70,970
Gross Unrealized Gains 49 32
Gross Unrealized Losses   (1)
Estimated Fair Value 50,697 71,001
Cash [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 37,721 55,079
Estimated Fair Value 37,721 55,079
Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 945 3,654
Estimated Fair Value 945 3,654
Cash and Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 38,666 58,733
Estimated Fair Value 38,666 58,733
U.S. Treasury Notes and Bonds - Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 4,753 503
Gross Unrealized Gains 6  
Gross Unrealized Losses   (1)
Estimated Fair Value 4,759 502
U.S. Treasury Notes and Bonds - Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,750 7,756
Gross Unrealized Gains 11 6
Estimated Fair Value 2,761 7,762
U.S. Government Agency Issues Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 1,000 1,001
Gross Unrealized Gains 1 1
Estimated Fair Value 1,001 1,002
U.S. Government Agency Issues Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 3,479 2,977
Gross Unrealized Gains 31 25
Estimated Fair Value $ 3,510 $ 3,002