Quarterly report pursuant to Section 13 or 15(d)

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

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Fair Value Measurements - Summary of Available-for-Sale Securities (Detail) (USD $)
In Thousands, unless otherwise specified
Apr. 30, 2014
Jan. 31, 2014
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost $ 116,583 $ 128,085
Gross Unrealized Gains 24 18
Gross Unrealized Losses      
Estimated Fair Value 116,607 128,103
Cash [Member]
    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 100,756 112,271
Gross Unrealized Gains      
Gross Unrealized Losses      
Estimated Fair Value 100,756 112,271
Cash Equivalents [Member]
    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,501 3,463
Gross Unrealized Gains      
Gross Unrealized Losses      
Estimated Fair Value 2,501 3,463
Cash and Cash Equivalents [Member]
    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 103,257 115,734
Gross Unrealized Gains      
Gross Unrealized Losses      
Estimated Fair Value 103,257 115,734
U.S. Treasury Notes and Bonds - Short Term [Member]
    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 3,523 3,540
Gross Unrealized Gains 4 5
Gross Unrealized Losses      
Estimated Fair Value 3,527 3,545
U.S. Government Agency Issues Short Term [Member]
    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 3,530 2,005
Gross Unrealized Gains 9 5
Gross Unrealized Losses      
Estimated Fair Value 3,539 2,010
U.S. Government Agency Issues Long Term [Member]
    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 6,273 6,806
Gross Unrealized Gains 11 8
Gross Unrealized Losses      
Estimated Fair Value $ 6,284 $ 6,814