Stock-Based Compensation - Summary of Activity for RSUs (Detail) - $ / shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted Average Grant Date Fair Value, Granted	$ 23.88	$ 16.04	$ 21.74
Stock Incentive Plan 2014 [Member] \| Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
RSUs/SARs, beginning of period	1,102,533
Granted	309,435
Vested	(737,007)
Forfeited or expired	(69,504)
RSUs/SARs, end of period	606,086	1,102,533
RSUs/SARs, Weighted Average Grant Date Fair Value, Beginning of period	$ 85.93
Weighted Average Grant Date Fair Value, Granted	98.72
Weighted Average Grant Date Fair Value, Vested	85.32
Weighted Average Grant Date Fair Value, Forfeited	85.71
RSUs/SARs, Weighted Average Grant Date Fair Value, end of period	$ 93.26	$ 85.93
Stock Incentive Plan 2014 [Member] \| Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Accrued dividend shares	629
Weighted Average Grant Date Fair Value, Accrued dividend shares	$ 114.35

Share amount for share-based compensation arrangement by share-based payment award equity instruments accrued dividend.

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- Definition

Per share amount share based compensation arrangement by share based payment award equity instruments other than options accrued dividend equivalents weighted average grant date fair value.

+ References

No definition available.

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- Definition

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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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- Definition

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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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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-Publisher FASB
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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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