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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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The cash inflow from the additional capital contribution to the entity.

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Amount of noncash expense for share-based payment arrangement.

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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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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Price of a single share of a number of saleable stocks of a company.

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Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Dec. 08, 2020	Jul. 19, 2019	May 03, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stockholders Equity Note Disclosure [Line Items]
Common stock, shares issued	1,725,000	1,587,000	3,144,531	54,760,837	52,078,258
Common stock issue price per share	$ 181.00	$ 87.00	$ 64.00
Exercised number of shares				340,546
Net proceeds from public offering	$ 297,800	$ 131,100	$ 189,600	$ 297,775	$ 320,713
Stock-based compensation expense				$ 17,007	$ 12,847	$ 10,192
Stock options, outstanding				696,711	957,559
Aggregate intrinsic value of stock options exercised				$ 36,600	$ 5,500	$ 5,300
Weighted average grant date fair value of share-based awards granted				$ 53.06	$ 31.27	$ 18.90
Total fair value of stock options vested				$ 2,800	$ 3,100	$ 2,300
Total unrecognized compensation cost				$ 46,700
Unrecognized compensation cost, weighted average remaining requisite service period				3 years 6 months 18 days
Number of unvested options and restricted stock units				1,853,028
2018 Plan
Stockholders Equity Note Disclosure [Line Items]
Common stock shares reserved for Issuance						2,778,000
Incentive options, vesting period				2,306,943
Employee Stock Option \| Minimum \| Vest Over Three Year
Stockholders Equity Note Disclosure [Line Items]
Incentive options, vesting percentage				20.00%
Employee Stock Option \| Maximum \| Vest Over Five Year
Stockholders Equity Note Disclosure [Line Items]
Incentive options, vesting percentage				33.00%
Option To Purchase Common Stock
Stockholders Equity Note Disclosure [Line Items]
Stock options, outstanding				696,711	957,559	998,226
Restricted Stock Units (RSUs)
Stockholders Equity Note Disclosure [Line Items]
Restricted stock units, outstanding				665,540	734,984	705,413
Closing price of common stock				$ 191.63
Aggregate intrinsic value of restricted stock units vested				$ 28,300	$ 17,500	$ 6,200
Weighted average grant date fair value of restricted stock units granted				$ 109.69	$ 49.68	$ 30.30
Total grant date fair value of restricted stock units vested				$ 10,800	$ 8,500	$ 4,600
Underwriters \| Common Stock
Stockholders Equity Note Disclosure [Line Items]
Exercised number of shares	225,000	207,000	410,156