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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate number of common shares reserved for future issuance.

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Description of common stock conversion feature. Includes, but is not limited to, conversion price; conversion right; timing of right; terms, event or change in circumstance causing contingency to be met or adjustment to conversion price or number of shares; manner of settlement upon conversion; and method of settlement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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Amount of cost to be recognized for option under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Description of terms of share-based payment arrangement. Includes, but is not limited to, type of award or grantee and reason for issuance.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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

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Percentage of vesting of award under share-based payment arrangement.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Purchase price of common stock expressed as a percentage of its fair value.

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Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018	Apr. 30, 2019	Jan. 31, 2019	Jan. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate intrinsic value of exercised options			$ 4,500	$ 27,500
Aggregate estimated fair value of stock options granted to employees vested			$ 2,400	$ 5,600
Weighted-average grant date fair value of options granted to employees			$ 8.00	$ 8.24
Unrecognized stock-based compensation expense related to stock option	$ 6,800		$ 6,800
Remaining weighted-average period			2 years 5 months 8 days
Stock options outstanding	9,195,826		9,195,826			9,096,961
Unrecognized stock-based compensation expense	$ 3,300		$ 3,300		$ 7,200
Share-based compensation expense	37,758	$ 31,790	$ 106,925	$ 89,086
Common Stock, trading day			On June 14, 2018, all of our outstanding shares of Class B common stock automatically converted into the same number of shares of Class A common stock pursuant to the terms of our Amended and Restated Certificate of Incorporation. No additional shares of Class B common stock will be issued following such conversion. The conversion occurred pursuant to Article IV of the Amended and Restated Certificate of Incorporation, which provided that each one share of Class B common stock would convert automatically, without any further action, into one share of Class A common stock on the first trading day falling on or after the date on which the outstanding shares of Class B common stock represent less than 5% of the aggregate number of shares of the then outstanding Class A common stock and Class B common stock.
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividend yield		0.00%	0.00%	0.00%
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Remaining weighted-average period			2 years 10 months 2 days
Unrecognized stock-based compensation expense	304,600		$ 304,600
Performance-Based Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense related to stock option	$ 4,000		$ 4,000
Remaining weighted-average period			3 years 3 days
2015 Equity Incentive Plan \| Performance-Based Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options outstanding	1,375,000		1,375,000
2015 Equity Incentive Plan \| Time-Based Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			4 years
2015 Equity Incentive Plan \| Class A Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares common stock reserved for issuance	19,337,104		19,337,104				12,200,000
2015 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of eligible compensation allowed to employees to purchase shares at a discount	15.00%		15.00%
Description of offering period excluding initial offering period			The 2015 ESPP provides for 24-month offering periods beginning March 16 and September 16 of each year, and each offering period consists of four six-month purchase periods.
Purchase price of common stock, percentage			85.00%
Description of offering period resets			the offering period resets and the new lower price becomes the new offering price for a new 24 month offering period.
Unrecognized stock-based compensation expense	$ 21,100		$ 21,100
Dividend yield	0.00%	0.00%	0.00%	0.00%
2015 Employee Stock Purchase Plan \| Class A Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares common stock reserved for issuance	1,926,616		1,926,616				2,500,000
Fiscal 2020 Executive Bonus Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Description of offering period resets			certain offering periods reset and the new lower price became the new offering price for a new 24 month offering period
Unrecognized stock-based compensation expense	$ 1,800		$ 1,800
Equity incentive compensation description			The Fiscal 2020 Executive Bonus Plan provides opportunities for 100% equity incentive compensation payouts based on our actual achievement of pre-established corporate financial objectives, subject to review and a final approval by our Compensation Committee.
Share-based compensation expense			$ 2,700
Fiscal 2020 Executive Bonus Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Remaining weighted-average period			1 year
Fiscal 2020 Executive Bonus Plan \| Class A Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common Stock, trading day			The number of restricted stock units each participant will receive is equal to the dollar value of his or her actual award payment divided by the average closing price of a share of our Class A common stock for the 30-trading day period ending the last trading date before the grant date
One Year from Vesting Commencement Date \| 2015 Equity Incentive Plan \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage			25.00%
One Year from Vesting Commencement Date \| 2015 Equity Incentive Plan \| Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage			25.00%
One Year from Vesting Commencement Date \| 2015 Equity Incentive Plan \| Time-Based Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage			25.00%
Per Month after One Year of Vesting Commencement Date \| 2015 Equity Incentive Plan \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage			2.08%
Per Month after One Year of Vesting Commencement Date \| 2015 Equity Incentive Plan \| Time-Based Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage			2.08%
Per Quarter after One Year Of Vesting Commencement Date \| 2015 Equity Incentive Plan \| Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage			6.25%