Share-Based Compensation - Additional Information (Detail) - USD ($) shares in Thousands, $ in Millions	3 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value of stock options exercised	$ 9.4
Total fair value of stock options vested	3.4
Expected future pre-tax compensation expense, nonvested stock options	$ 22.8
Weighted average period to recognize expected future pre-tax compensation expense (in years)	2 years
Nonvested restricted stock outstanding (in shares)	600
Share-based payment arrangement, nonvested award, cost not yet recognized, amount	$ 12.9
Share-based payment award, options, outstanding (in shares)	4,311	3,950
Non vested Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested stock options outstanding (in shares)	2,100
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period to recognize expected future pre-tax compensation expense (in years)	2 years
Total fair value of vested restricted stock	$ 12.8
Expected future pre-tax compensation expense, nonvested restricted shares	$ 42.8
Nonvested restricted stock outstanding (in shares)	633	701
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested restricted stock outstanding (in shares)	295	264
Share-based payment award, options, outstanding (in shares)	300
Officers And Key Management Employees \| Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cliff vesting period	3 years
Minimum \| Officers And Key Management Employees \| Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, vesting rate	0.00%
Maximum \| Officers And Key Management Employees \| Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, vesting rate	200.00%

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

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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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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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Amount of cost to be recognized for option under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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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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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Number of options outstanding, including both vested and non-vested options.

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Percentage of vesting of award under share-based payment arrangement.

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Number of non-vested options outstanding.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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