Benefit Plans - Plan Assets Using Fair Value Methodologies (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 28.4	$ 34.4
Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		11.3
Total | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.3
Total | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.9	11.0
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.3
Level 1 | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.3
Level 1 | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Level 2 | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Level 2 | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		11.0
Level 3 | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Level 3 | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.9	11.0
Investments measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 16.5	$ 23.1