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

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Share-Based Compensation - Additional Information (Detail) - USD ($) shares in Thousands, $ in Millions	1 Months Ended	6 Months Ended
	Mar. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value of stock options exercised		$ 30.5
Total fair value of stock options vested		13.6
Expected future pre-tax compensation expense, nonvested stock options		$ 22.6
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		$ 9.7
Share-based payment award, options, outstanding (in shares)		3,935	3,950
Non vested Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested stock options outstanding (in shares)		1,400
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		$ 23.6
Expected future pre-tax compensation expense, nonvested restricted shares		$ 37.0
Nonvested restricted stock outstanding (in shares)		481	701
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested restricted stock outstanding (in shares)		292	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%