Quarterly report pursuant to Section 13 or 15(d)

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

v3.3.1.900
Fair Value Measurements - Summary of Available-for-Sale Securities (Detail) - USD ($)
$ in Thousands
Oct. 31, 2015
Jan. 31, 2015
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost $ 70,783 $ 104,285
Gross Unrealized Gains 21 43
Gross Unrealized Losses 0 0
Estimated Fair Value 70,804 104,328
Cash [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 54,901 88,444
Gross Unrealized Losses 0 0
Estimated Fair Value 54,901 88,444
Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 3,129 1,575
Gross Unrealized Losses 0 0
Estimated Fair Value 3,129 1,575
Cash and Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 58,030 90,019
Gross Unrealized Losses 0 0
Estimated Fair Value 58,030 90,019
U.S. Treasury Notes and Bonds - Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,003 1,500
Gross Unrealized Gains 1 1
Gross Unrealized Losses 0 0
Estimated Fair Value 2,004 1,501
U.S. Treasury Notes and Bonds - Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 6,761 4,268
Gross Unrealized Gains 4 18
Gross Unrealized Losses 0 0
Estimated Fair Value 6,765 4,286
U.S. Government Agency Issues Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,502 6,008
Gross Unrealized Gains 2 7
Gross Unrealized Losses 0 0
Estimated Fair Value 2,504 6,015
U.S. Government Agency Issues Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 1,487 2,490
Gross Unrealized Gains 14 17
Gross Unrealized Losses 0 0
Estimated Fair Value $ 1,501 $ 2,507