Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense recognized		$ 4.5	$ 2.6	$ 3.7
Stock-based compensation expense after tax		$ 3.4	$ 2.0	$ 2.5
Weighted-average fair value of options granted (in dollars per share)		$ 10.26	$ 11.62	$ 11.50
Aggregate intrinsic value of options exercised		$ 12.3	$ 20.6	$ 7.5
Total unrecognized compensation cost of nonvested stock options		$ 1.0
Expected weighted-average period		2 years 8 months 12 days
Non-Vested Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense recognized		$ 1.1
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense recognized		$ 3.0
Vesting period	4 years
Weighted average fair value, granted (in dollars per share)		$ 43.28	$ 48.38	$ 47.05
Total compensation cost to be recognized		$ 3.1
Weighted average remaining contractual term		2 years 6 months
Total fair value, vested		$ 1.5	$ 1.6	$ 1.2
Share-based Compensation Award, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted, vest in percentage per annum increments (as percent)		25.00%	25.00%	25.00%
Share-based Compensation Award, Tranche One | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance award vesting period		5 years
Share-based Compensation Award, Tranche One | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance award vesting period		7 years
Stock Incentive 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grants under 2013 Plan (in shares)		1,500,000
Shares reserved for future issuance (in shares)		1,129,687
Performance RSU Plan | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense recognized		$ 0.5