Equity Plans and Stock-based Compensation - Summary of stock option awards (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
Jul. 31, 2021	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock option awards outstanding beginning balance	30,166,792			28,955,341
Number of stock option awards granted		8,912,180	10,780,372	8,811,605
Number of stock option awards exercised	(3,292,219)	(11,042,592)	(4,830,469)	(3,853,935)
Number of stock option awards forfeited	(452,893)
Number of stock option awards expired	(19,963)	(2,585,875)	(2,728,460)	(2,250,990)
Number of stock option awards outstanding ending balance	26,401,717	30,167,177	34,883,464	31,662,021
Number of stock option awards options vested and expected to vest	25,667,621	27,483,800
Number of stock option awards exercisable	16,457,228	16,591,050
Weighted average exercise price outstanding beginning balance	$ 0.71	$ 0.65	$ 0.6	$ 0.59
Weighted average exercise price granted		0.75	0.75	0.57
Weighted average exercise price exercised	0.53	0.55	0.47	0.35
Weighted average exercise price forfeited	0.73
Weighted average exercise price expired	53.22	0.84	0.83	0.75
Weighted average exercise price outstanding ending balance	0.69	0.71	$ 0.65	$ 0.6
Weighted average exercise price options vested and expected to vest	0.69	0.69
Weighted average exercise price exercisable	$ 0.66	$ 0.68
Weighted average remaining contractual term	7 years	7 years 3 months 18 days	7 years 4 months 24 days	7 years 8 months 12 days
Weighted average remaining contractual term options vested and expected to vest	7 years	7 years 2 months 12 days
Weighted average remaining contractual term exercisable	6 years 3 months 18 days	6 years 4 months 24 days
Aggregate intrinsic value outstanding		$ 1,064,539			$ 8,905,754
Aggregate intrinsic value exercised		(110,643,446)	$ (3,464,262)	$ (1,364,006)
Aggregate intrinsic value options vested and expected to vest	$ 589,470	969,997,293
Aggregate intrinsic value exercisable	378,402	586,047,442
Aggregate intrinsic value outstanding	$ 606,280	$ 1,064,538,557	$ 19,314,017	$ 7,456,493

Share-based Compensation Arrangement by Share-based Payment Award, Option, Outstanding, Intrinsic Value

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Share-based Compensation Arrangement by Share-based Payment Award, Option, Outstanding, Number

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of share options (or share units) exercised during the current period.

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