Net Income per Share Attributable to Common Stockholders - Numerators and Denominators of the Basic and Diluted EPS Computations for Common Stock (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income	$ 9,578	$ 5,998	$ 16,799	$ 10,843
Weighted average shares used in computing net income per share attributable to common stockholders, basic	127,314	24,418	125,632	23,440
Net income per share attributable to common stockholders, basic	$ 0.07	$ 0.05	$ 0.13	$ 0.09
Reallocation as a result of conversion of Class B to Class A common stock:
Number of shares used for basic EPS computation	127,314	24,418	125,632	23,440
Weighted average shares used in computing net income per share attributable to common stockholders, diluted	143,353	37,038	143,506	35,833
Net income per share attributable to common stockholders, diluted	$ 0.07	$ 0.03	$ 0.12	$ 0.06
Class A common stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income	3,330		4,428
Undistributed earnings allocated to participating securities	(31)		(41)
Net income attributable to common stockholders, basic	3,299		4,387
Weighted average shares used in computing net income per share attributable to common stockholders, basic	44,261		33,113
Net income per share attributable to common stockholders, basic	$ 0.07		$ 0.13
Net income attributable to common stockholders, basic	3,299		4,387
Reallocation as a result of conversion of Class B to Class A common stock:
Net income attributable to common stockholders, basic	6,191		12,256
Net income attributable to common stockholders, diluted	9,490		16,643
Number of shares used for basic EPS computation	44,261		33,113
Conversion of Class B to Class A common stock	83,053		92,519
Effect of potentially dilutive common shares	16,039		17,874
Weighted average shares used in computing net income per share attributable to common stockholders, diluted	143,353		143,506
Net income per share attributable to common stockholders, diluted	$ 0.07		$ 0.12
Class B common stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income	6,248	5,998	12,371	10,843
Noncumulative dividends on convertible preferred stock		(140)		(280)
Undistributed earnings allocated to participating securities	(57)	(4,583)	(115)	(8,341)
Net income attributable to common stockholders, basic	6,191	1,275	12,256	2,222
Weighted average shares used in computing net income per share attributable to common stockholders, basic	83,053	24,418	92,519	23,440
Net income per share attributable to common stockholders, basic	$ 0.07	$ 0.05	$ 0.13	$ 0.09
Net income attributable to common stockholders, basic	6,191	1,275	12,256	2,222
Reallocation as a result of conversion of Class B to Class A common stock:
Reallocation of net income to Class B common stock	369		546
Net income attributable to common stockholders, diluted	$ 6,560	$ 1,275	$ 12,802	$ 2,222
Number of shares used for basic EPS computation	83,053	24,418	92,519	23,440
Effect of potentially dilutive common shares	16,039	12,620	17,874	12,393
Weighted average shares used in computing net income per share attributable to common stockholders, diluted	99,092	37,038	110,393	35,833
Net income per share attributable to common stockholders, diluted	$ 0.07	$ 0.03	$ 0.12	$ 0.06