Share-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions				12 Months Ended
	May 19, 2020	Feb. 25, 2020	May 15, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Nov. 09, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Options, granted (in shares)				2,108,950	1,315,975	4,140,800
Vesting period (in years)				4 years
Options outstanding (in shares)				8,744,765	7,008,403
Weighted average exercise price (in dollars per share)				$ 20.42	$ 23.34
Share-based compensation not yet recognized, stock options				$ 32.7
Share-based compensation not yet recognized, period for recognition (in years)				2 years 4 months 20 days
Common Stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Tax benefit from compensation expense				$ 4.3	$ 4.7	$ 4.7
Intrinsic value of options exercised				$ 0.1	$ 0.1	$ 2.4
Amended and Restated 2018 Long Term Incentive Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Number of additional shares authorized (in shares)	1,500,000
Authorized shares for issuance (in shares)	3,300,000
2018 Long Term Incentive Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Number of additional shares authorized (in shares)			1,177,933
Maximum Number of Shares to be Issued - ISO Exercise (in shares)				2,500,000			2,500,000
Grant period (in years)				10 years
Number of shares available for grant (in shares)				1,669,619
Weighted average exercise price (in dollars per share)							$ 17.63
Amended and Restated 2012 Long Term Incentive Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Grant period (in years)				10 years
2020 Employment Inducement Incentive Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Number of additional shares authorized (in shares)				710,000
Authorized shares for issuance (in shares)				710,000
Grant period (in years)		10 years
Number of shares available for grant (in shares)				0