Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, employer contributions			$ 1.1
Supplemental Executive Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, employer contributions		$ 2.1	2.9
Obligations under the supplemental plan		$ 19.3	$ 19.3	$ 21.4
Supplemental Executive Retirement Plan | Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, employer contributions	$ 0.4