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
Oct. 31, 2016
Jan. 31, 2016
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost $ 37,725 $ 70,970
Gross Unrealized Gains 30 32
Gross Unrealized Losses (1) (1)
Estimated Fair Value 37,754 71,001
Cash [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 24,763 55,079
Estimated Fair Value 24,763 55,079
Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,721 3,654
Estimated Fair Value 2,721 3,654
Cash and Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 27,484 58,733
Estimated Fair Value 27,484 58,733
U.S. Treasury Notes and Bonds - Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 4,250 503
Gross Unrealized Gains 6  
Gross Unrealized Losses   (1)
Estimated Fair Value 4,256 502
U.S. Treasury Notes and Bonds - Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,004 7,756
Gross Unrealized Gains 1 6
Gross Unrealized Losses (1)  
Estimated Fair Value 2,004 7,762
U.S. Government Agency Issues Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost   1,001
Gross Unrealized Gains   1
Estimated Fair Value   1,002
U.S. Government Agency Issues Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 3,987 2,977
Gross Unrealized Gains 23 25
Estimated Fair Value $ 4,010 $ 3,002