Allocation of Plan Assets by Investments (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	$ 3,115.2	$ 4,094.5	$ 3,793.4
Level 1
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	88.0	83.0
Level 2
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	375.5	427.8
Fair Value Inputs Level 1 And Level 2 [Member]
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	463.5	510.8
MEASURED AT NAV
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	2,651.7	3,583.7
U.S. Equities
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	830.9	1,125.7
U.S. Equities | MEASURED AT NAV
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	830.9	1,125.7
Global Equities
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	795.9	1,240.8
Global Equities | MEASURED AT NAV
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	795.9	1,240.8
Total Equities
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	$ 1,626.8	$ 2,366.5
Total Equities | Minimum
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Equity funds, target	50.00%	50.00%
Total Equities | Maximum
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Equity funds, target	70.00%	70.00%
Total Equities | MEASURED AT NAV
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	$ 1,626.8	$ 2,366.5
U.S. Fixed Income
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	945.4	1,182.8
U.S. Fixed Income | Level 1
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	82.2	75.9
U.S. Fixed Income | Level 2
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	258.0	303.0
U.S. Fixed Income | Fair Value Inputs Level 1 And Level 2 [Member]
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	340.2	378.9
U.S. Fixed Income | MEASURED AT NAV
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	605.2	803.9
Non-U.S. Fixed Income
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	450.8	447.3
Non-U.S. Fixed Income | Level 2
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	31.4	35.1
Non-U.S. Fixed Income | Fair Value Inputs Level 1 And Level 2 [Member]
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	31.4	35.1
Non-U.S. Fixed Income | MEASURED AT NAV
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	419.4	412.2
Total Fixed Income
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	$ 1,396.2	$ 1,630.1
Total Fixed Income | Minimum
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Equity funds, target	30.00%	30.00%
Total Fixed Income | Maximum
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Equity funds, target	50.00%	50.00%
Total Fixed Income | Level 1
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	$ 82.2	$ 75.9
Total Fixed Income | Level 2
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	289.4	338.1
Total Fixed Income | Fair Value Inputs Level 1 And Level 2 [Member]
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	371.6	414.0
Total Fixed Income | MEASURED AT NAV
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	1,024.6	1,216.1
Cash and Other
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	92.2	97.9
Cash and Other | Level 1
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	5.8	7.1
Cash and Other | Level 2
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	86.1	89.7
Cash and Other | Fair Value Inputs Level 1 And Level 2 [Member]
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	91.9	96.8
Cash and Other | MEASURED AT NAV
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	$ 0.3	$ 1.1