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		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income	$ 12,958	$ 13,406	$ 25,467	$ 26,388
Weighted average shares used in computing net income per share attributable to common stockholders, basic	135,126	131,799	134,531	131,455
Net income per share attributable to common stockholders, basic	$ 0.10	$ 0.10	$ 0.19	$ 0.20
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	147,155	144,871	146,690	144,870
Net income per share attributable to common stockholders, diluted	$ 0.09	$ 0.09	$ 0.17	$ 0.18
Class A common stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income	$ 9,381	$ 7,450	$ 17,787	$ 14,292
Undistributed earnings allocated to participating securities	(1)	(9)	(1)	(17)
Net income attributable to common stockholders, basic	$ 9,380	$ 7,441	$ 17,786	$ 14,275
Weighted average shares used in computing net income per share attributable to common stockholders, basic	97,823	73,246	93,961	71,197
Net income per share attributable to common stockholders, basic	$ 0.10	$ 0.10	$ 0.19	$ 0.20
Net income attributable to common stockholders, basic	$ 9,380	$ 7,441	$ 17,786	$ 14,275
Reallocation as a result of conversion of Class B to Class A common stock:
Net income attributable to common stockholders, basic	3,577	5,949	7,679	12,082
Net income attributable to common stockholders, diluted	$ 12,957	$ 13,390	$ 25,465	$ 26,357
Conversion of Class B to Class A common stock	37,303	58,553	40,570	60,258
Effect of potentially dilutive common shares	12,029	13,072	12,159	13,415
Weighted average shares used in computing net income per share attributable to common stockholders, diluted	147,155	144,871	146,690	144,870
Net income per share attributable to common stockholders, diluted	$ 0.09	$ 0.09	$ 0.17	$ 0.18
Class B common stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income	$ 3,577	$ 5,956	$ 7,680	$ 12,096
Undistributed earnings allocated to participating securities		(7)	(1)	(14)
Net income attributable to common stockholders, basic	$ 3,577	$ 5,949	$ 7,679	$ 12,082
Weighted average shares used in computing net income per share attributable to common stockholders, basic	37,303	58,553	40,570	60,258
Net income per share attributable to common stockholders, basic	$ 0.10	$ 0.10	$ 0.19	$ 0.20
Net income attributable to common stockholders, basic	$ 3,577	$ 5,949	$ 7,679	$ 12,082
Reallocation as a result of conversion of Class B to Class A common stock:
Reallocation of net income to Class B common stock	767	671	1,474	1,322
Net income attributable to common stockholders, diluted	$ 4,344	$ 6,620	$ 9,153	$ 13,404
Effect of potentially dilutive common shares	12,029	13,072	12,159	13,415
Weighted average shares used in computing net income per share attributable to common stockholders, diluted	49,332	71,625	52,729	73,673
Net income per share attributable to common stockholders, diluted	$ 0.09	$ 0.09	$ 0.17	$ 0.18