Quarterly report pursuant to Section 13 or 15(d)

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

v3.2.0.727
Fair Value Measurements - Summary of Available-for-Sale Securities (Detail) - USD ($)
$ in Thousands
Jul. 31, 2015
Jan. 31, 2015
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost $ 72,815 $ 104,285
Gross Unrealized Gains 28 43
Gross Unrealized Losses 0 0
Estimated Fair Value 72,843 104,328
Cash [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 56,933 88,444
Gross Unrealized Losses 0 0
Estimated Fair Value 56,933 88,444
Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 3,627 1,575
Gross Unrealized Losses 0 0
Estimated Fair Value 3,627 1,575
Cash and Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 60,560 90,019
Gross Unrealized Losses 0 0
Estimated Fair Value 60,560 90,019
U.S. Treasury Notes and Bonds - Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,004 1,500
Gross Unrealized Gains 2 1
Gross Unrealized Losses 0 0
Estimated Fair Value 2,006 1,501
U.S. Treasury Notes and Bonds - Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 5,760 4,268
Gross Unrealized Gains 10 18
Gross Unrealized Losses 0 0
Estimated Fair Value 5,770 4,286
U.S. Government Agency Issues Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,002 6,008
Gross Unrealized Gains 1 7
Gross Unrealized Losses 0 0
Estimated Fair Value 2,003 6,015
U.S. Government Agency Issues Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,489 2,490
Gross Unrealized Gains 15 17
Gross Unrealized Losses 0 0
Estimated Fair Value $ 2,504 $ 2,507