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		9 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income	$ 21,630	$ 10,482	$ 47,097	$ 36,870
Weighted average shares used in computing net income per share attributable to common stockholders, basic	135,624	132,413	135,144	131,731
Net income per share attributable to common stockholders, basic	$ 0.16	$ 0.08	$ 0.35	$ 0.28
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	147,436	145,063	147,073	144,909
Net income per share attributable to common stockholders, diluted	$ 0.15	$ 0.07	$ 0.32	$ 0.25
Class A common stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income	$ 16,190	$ 6,156	$ 33,637	$ 20,545
Undistributed earnings allocated to participating securities		(5)	(1)	(21)
Net income attributable to common stockholders, basic	$ 16,190	$ 6,151	$ 33,636	$ 20,524
Weighted average shares used in computing net income per share attributable to common stockholders, basic	101,514	77,759	96,521	73,405
Net income per share attributable to common stockholders, basic	$ 0.16	$ 0.08	$ 0.35	$ 0.28
Net income attributable to common stockholders, basic	$ 16,190	$ 6,151	$ 33,636	$ 20,524
Reallocation as a result of conversion of Class B to Class A common stock:
Net income attributable to common stockholders, basic	5,440	4,322	13,459	16,308
Net income attributable to common stockholders, diluted	$ 21,630	$ 10,473	$ 47,095	$ 36,832
Conversion of Class B to Class A common stock	34,110	54,654	38,623	58,326
Effect of potentially dilutive common shares	11,812	12,650	11,929	13,178
Weighted average shares used in computing net income per share attributable to common stockholders, diluted	147,436	145,063	147,073	144,909
Net income per share attributable to common stockholders, diluted	$ 0.15	$ 0.07	$ 0.32	$ 0.25
Class B common stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income	$ 5,440	$ 4,326	$ 13,460	$ 16,325
Undistributed earnings allocated to participating securities		(4)	(1)	(17)
Net income attributable to common stockholders, basic	$ 5,440	$ 4,322	$ 13,459	$ 16,308
Weighted average shares used in computing net income per share attributable to common stockholders, basic	34,110	54,654	38,623	58,326
Net income per share attributable to common stockholders, basic	$ 0.16	$ 0.08	$ 0.35	$ 0.28
Net income attributable to common stockholders, basic	$ 5,440	$ 4,322	$ 13,459	$ 16,308
Reallocation as a result of conversion of Class B to Class A common stock:
Reallocation of net income to Class B common stock	1,297	537	2,728	1,867
Net income attributable to common stockholders, diluted	$ 6,737	$ 4,859	$ 16,187	$ 18,175
Effect of potentially dilutive common shares	11,812	12,650	11,929	13,178
Weighted average shares used in computing net income per share attributable to common stockholders, diluted	45,922	67,304	50,552	71,504
Net income per share attributable to common stockholders, diluted	$ 0.15	$ 0.07	$ 0.32	$ 0.25