Equity Incentive Plans - Summary of Fair Value of ESPP Purchase Rights Was Estimated Using Black-Scholes Option-pricing Model Assumptions (Details) - $ / shares	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Volatility			40.00%
Expected dividend yield	0.00%	0.00%	0.00%
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair market value of common stock		$ 151.76	$ 79.25
Expected term		6 years	6 years
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair market value of common stock		$ 66.26	$ 39.76
Expected term		5 years	5 years
2018 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Volatility			40.00%
Expected term	6 months	6 months	6 months
Expected dividend yield	0.00%	0.00%	0.00%
2018 Employee Stock Purchase Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair market value of common stock	$ 166.84	$ 138.83	$ 82.12
Volatility	34.00%	49.00%
Risk-free interest rate	0.08%	1.54%	2.59%
2018 Employee Stock Purchase Plan \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair market value of common stock	$ 152.35	$ 87.23	$ 40.60
Volatility	31.00%	32.00%
Risk-free interest rate	0.06%	0.11%	2.04%

Fair value of common stock.

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- Definition

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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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

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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- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
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-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=122041274&loc=d3e301413-122809

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