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Share-Based Compensation - Additional Information (Detail) - USD ($) shares in Thousands, $ in Millions	1 Months Ended	9 Months Ended
	Mar. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value of stock options exercised		$ 40.7
Total fair value of stock options vested		13.7
Expected future pre-tax compensation expense, nonvested stock options		$ 16.4
Weighted average period to recognize expected future pre-tax compensation expense		2 years
Nonvested restricted stock outstanding (in shares)		500
Share-based payment arrangement, nonvested award, cost not yet recognized, amount		$ 7.3
Share-based payment award, options, outstanding (in shares)		3,731	3,950
Non vested Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested stock options outstanding (in shares)		1,300
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period to recognize expected future pre-tax compensation expense		2 years
Total fair value of vested restricted stock		$ 24.1
Expected future pre-tax compensation expense, nonvested restricted shares		$ 32.6
Nonvested restricted stock outstanding (in shares)		464	701
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period to recognize expected future pre-tax compensation expense		1 year
Nonvested restricted stock outstanding (in shares)		291	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%