Net Income per Share Attributable to Common Stockholders - Numerators and Denominators of the Basic and Diluted EPS Computations for Common Stock (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended
Apr. 30, 2018
Apr. 30, 2017
Schedule Of Earnings Per Share Basic And Diluted [Line Items]    
Net income $ 44,310 $ 36,996 [1]
Weighted average shares used in computing net income per share attributable to common stockholders, basic 142,777 137,096 [1]
Net income per share attributable to common stockholders, basic $ 0.31 $ 0.27 [1]
Reallocation as a result of conversion of Class B to Class A common stock:    
Weighted average shares used in computing net income per share attributable to common stockholders, diluted 154,935 151,056 [1]
Net income per share attributable to common stockholders, diluted $ 0.29 $ 0.24 [1]
Class A common stock [Member]    
Schedule Of Earnings Per Share Basic And Diluted [Line Items]    
Net income $ 36,830  
Net income attributable to common stockholders, basic $ 36,830  
Weighted average shares used in computing net income per share attributable to common stockholders, basic 118,675  
Net income per share attributable to common stockholders, basic $ 0.31  
Net income attributable to common stockholders, basic $ 36,830  
Reallocation as a result of conversion of Class B to Class A common stock:    
Net income attributable to common stockholders, basic 7,480  
Net income attributable to common stockholders, diluted $ 44,310  
Conversion of Class B to Class A common stock 24,102  
Effect of potentially dilutive common shares 12,158  
Weighted average shares used in computing net income per share attributable to common stockholders, diluted 154,935  
Net income per share attributable to common stockholders, diluted $ 0.29  
Class A common stock [Member] | As adjusted [Member]    
Schedule Of Earnings Per Share Basic And Diluted [Line Items]    
Net income [1]   $ 28,420
Net income attributable to common stockholders, basic [1]   $ 28,420
Weighted average shares used in computing net income per share attributable to common stockholders, basic [1]   106,524
Net income per share attributable to common stockholders, basic [1]   $ 0.27
Net income attributable to common stockholders, basic [1]   $ 28,420
Reallocation as a result of conversion of Class B to Class A common stock:    
Net income attributable to common stockholders, basic [1]   8,576
Net income attributable to common stockholders, diluted [1]   $ 36,996
Conversion of Class B to Class A common stock [1]   32,146
Effect of potentially dilutive common shares [1]   13,960
Weighted average shares used in computing net income per share attributable to common stockholders, diluted [1]   152,630
Net income per share attributable to common stockholders, diluted [1]   $ 0.24
Class B common stock [Member]    
Schedule Of Earnings Per Share Basic And Diluted [Line Items]    
Net income $ 7,480  
Net income attributable to common stockholders, basic $ 7,480  
Weighted average shares used in computing net income per share attributable to common stockholders, basic 24,102  
Net income per share attributable to common stockholders, basic $ 0.31  
Net income attributable to common stockholders, basic $ 7,480  
Reallocation as a result of conversion of Class B to Class A common stock:    
Reallocation of net income to Class B common stock 2,890  
Net income attributable to common stockholders, diluted $ 10,370  
Effect of potentially dilutive common shares 12,158  
Weighted average shares used in computing net income per share attributable to common stockholders, diluted 36,260  
Net income per share attributable to common stockholders, diluted $ 0.29  
Class B common stock [Member] | As adjusted [Member]    
Schedule Of Earnings Per Share Basic And Diluted [Line Items]    
Net income [1]   $ 8,576
Net income attributable to common stockholders, basic [1]   $ 8,576
Weighted average shares used in computing net income per share attributable to common stockholders, basic [1]   32,146
Net income per share attributable to common stockholders, basic [1]   $ 0.27
Net income attributable to common stockholders, basic [1]   $ 8,576
Reallocation as a result of conversion of Class B to Class A common stock:    
Reallocation of net income to Class B common stock [1]   2,600
Net income attributable to common stockholders, diluted [1]   $ 11,176
Effect of potentially dilutive common shares [1]   13,960
Weighted average shares used in computing net income per share attributable to common stockholders, diluted [1]   46,106
Net income per share attributable to common stockholders, diluted [1]   $ 0.24
[1] See note 1 of the notes to the condensed consolidated financial statements for a summary of adjustments.