Stockholders' Equity (Deficit) - Summary of Activity for Non-vested Three-year PSU awards (Detail) - $ / shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Shares
Vested (in shares)	(315,902)	(164,347)	(151,280)
Three-year PSU Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU awards performance period	3 years	3 years	3 years
Shares
Non-vested at beginning of period (in shares)	370,703
Granted (in shares)	323,135
Vested (in shares)	(189,445)
Forfeited or expired (in shares)	(16,937)
Non-vested at end of period (in shares)	487,456	370,703
Weighted-Average per Share Fair Value on Grant Date
Non-vested, beginning of period (in dollars per share)	$ 45.08
Granted (in dollars per share)	36.33
Vested (in dollars per share)	42.07
Forfeited or expired (in dollars per share)	42.64
Non-vested, end of period (in dollars per share)	$ 40.41	$ 45.08

Performance stock unit award period.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The number of grants made 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 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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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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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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Weighted average grant-date fair value of non-vested options forfeited.

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