Net Income per Share - 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, 2020	Apr. 30, 2019
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Weighted average shares used in computing net income per share, basic	149,541	146,708
Net income per share attributable to common stockholders, basic (in usd per share)	$ 0.58	$ 0.50
Reallocation as a result of conversion of Class B to Class A common stock:
Weighted average shares used in computing net income per share, diluted	159,474	157,910
Net income per share attributable to common stockholders, diluted (in usd per share)	$ 0.54	$ 0.47
Class A common stock
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income, basic	$ 77,777	$ 63,652
Weighted average shares used in computing net income per share, basic	134,353	127,139
Net income per share attributable to common stockholders, basic (in usd per share)	$ 0.58	$ 0.50
Net income, basic	$ 77,777	$ 63,652
Reallocation as a result of conversion of Class B to Class A common stock:
Net income, basic	8,793	9,797
Reallocation of net income to Class B common stock	0
Net income, diluted	$ 86,570	$ 73,449
Conversion of Class B to Class A common stock	15,188	19,569
Effect of potentially dilutive common shares	9,933	11,202
Weighted average shares used in computing net income per share, diluted	159,474	157,910
Net income per share attributable to common stockholders, diluted (in usd per share)	$ 0.54	$ 0.47
Class B common stock
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income, basic	$ 8,793	$ 9,797
Weighted average shares used in computing net income per share, basic	15,188	19,569
Net income per share attributable to common stockholders, basic (in usd per share)	$ 0.58	$ 0.50
Net income, basic	$ 8,793	$ 9,797
Reallocation as a result of conversion of Class B to Class A common stock:
Net income, basic	0	0
Reallocation of net income to Class B common stock	4,844	4,516
Net income, diluted	$ 13,637	$ 14,313
Conversion of Class B to Class A common stock	0	0
Effect of potentially dilutive common shares	9,933	11,202
Weighted average shares used in computing net income per share, diluted	25,121	30,771
Net income per share attributable to common stockholders, diluted (in usd per share)	$ 0.54	$ 0.47