Pension and Other Employee Benefits - Schedule Fair Value of Pension Plan Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total assets at fair value	$ 13.3	$ 12.9	$ 11.4
Fixed income [Member] | Level 1 [Member]
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total assets at fair value	3.8	3.8	3.5
Other Private Investments [Member] | Level 3 [Member]
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total assets at fair value	4.2	3.9	3.2
Investment grade [Member] | Level 2 [Member]
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total assets at fair value	4.3	4.4	3.9
Cash and cash equivalents [Member] | Level 1 [Member]
Defined Benefit Pension Plan With Accumulated Benefit Obligation In Excess Of Fair Value Of Plan Assets [Line Items]
Total assets at fair value	$ 1.0	$ 0.8	$ 0.8