Stock Compensation - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 3.3	$ 5.1
Aggregate weighted-average grant-date fair value of units granted	24.1	16.4
Total unrecognized compensation cost	$ 29.8
Unrecognized compensation cost, weighted-average recognition period	2 years 7 months 6 days
Aggregate weighted-average grant-date fair value of units vested	$ 14.0	$ 11.8
Performance-Based Units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares which will vest after achievement of goals (in shares)	0
Performance-Based Units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares which will vest after achievement of goals (in shares)	2

Share Based Compensation Arrangement By Share Based Payment Award Number of Shares Vesting After Achievement of Goals

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- Definition

Share-based compensation arrangement by share-based payment award, other than options, grants in period, weighted average grant date fair value.

+ References

No definition available.

+ Details

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- Definition

Share-based compensation arrangement by share-based payment award, other than options, vested in period, weighted average grant date fair value.

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Section 50
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-Name Accounting Standards Codification
-Topic 718
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-Section S99
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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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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- 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.

+ References

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