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.