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		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Weighted average shares used in computing net income per share, basic	148,157	144,737	147,467	143,765
Net income per share attributable to common stockholders, basic (in usd per share)	$ 0.56	$ 0.44	$ 1.59	$ 1.10
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	158,750	156,025	158,124	155,706
Net income per share attributable to common stockholders, diluted (in usd per share)	$ 0.52	$ 0.41	$ 1.49	$ 1.02
Class A common stock
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income, basic	$ 73,120		$ 206,862
Weighted average shares used in computing net income per share, basic	131,720		129,845
Net income per share attributable to common stockholders, basic (in usd per share)	$ 0.56		$ 1.59
Net income, basic	$ 73,120		$ 206,862
Reallocation as a result of conversion of Class B to Class A common stock:
Net income, basic	9,125		28,074
Reallocation of net income to Class B common stock	0		0
Net income, diluted	$ 82,245		$ 234,936
Conversion of Class B to Class A common stock	16,437		17,622
Effect of potentially dilutive common shares	10,593		10,657
Weighted average shares used in computing net income per share, diluted	158,750		158,124
Net income per share attributable to common stockholders, diluted (in usd per share)	$ 0.52		$ 1.49
Class A common stock | As adjusted
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income, basic		$ 54,592		$ 133,568
Weighted average shares used in computing net income per share, basic		123,297		121,013
Net income per share attributable to common stockholders, basic (in usd per share)		$ 0.44		$ 1.10
Net income, basic		$ 54,592		$ 133,568
Reallocation as a result of conversion of Class B to Class A common stock:
Net income, basic		9,493		25,113
Reallocation of net income to Class B common stock				0
Net income, diluted		$ 64,085		$ 158,681
Conversion of Class B to Class A common stock		21,440		22,752
Effect of potentially dilutive common shares		11,288		11,941
Weighted average shares used in computing net income per share, diluted		156,025		155,706
Net income per share attributable to common stockholders, diluted (in usd per share)		$ 0.41		$ 1.02
Class B common stock
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income, basic	$ 9,125		$ 28,074
Weighted average shares used in computing net income per share, basic	16,437		17,622
Net income per share attributable to common stockholders, basic (in usd per share)	$ 0.56		$ 1.59
Net income, basic	$ 9,125		$ 28,074
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	4,879		13,942
Net income, diluted	$ 14,004		$ 42,016
Conversion of Class B to Class A common stock	0		0
Effect of potentially dilutive common shares	10,593		10,657
Weighted average shares used in computing net income per share, diluted	27,030		28,279
Net income per share attributable to common stockholders, diluted (in usd per share)	$ 0.52		$ 1.49
Class B common stock | As adjusted
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income, basic		$ 9,493		$ 25,113
Weighted average shares used in computing net income per share, basic		21,440		22,752
Net income per share attributable to common stockholders, basic (in usd per share)		$ 0.44		$ 1.10
Net income, basic		$ 9,493		$ 25,113
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		3,950		10,243
Net income, diluted		$ 13,443		$ 35,356
Conversion of Class B to Class A common stock		0		0
Effect of potentially dilutive common shares		11,288		11,941
Weighted average shares used in computing net income per share, diluted		32,728		34,693
Net income per share attributable to common stockholders, diluted (in usd per share)		$ 0.41		$ 1.02