Employee Benefits - Narrative (Detail)	1 Months Ended	6 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2024 USD ($)	Jun. 30, 2022	Jun. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2023 USD ($) investment numberOfDerivativeInstruments	Dec. 31, 2022 USD ($) numberOfDerivativeInstruments	Dec. 31, 2021 USD ($)	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Actuarial Loss (Gain)						$ 53,300,000	$ (365,500,000)
Estimated contribution defined contribution plans						$ 72,400,000	$ 67,200,000	$ 65,300,000
Number of investments held in diversified portfolios | investment						1
Number of derivatives held by the plan | numberOfDerivativeInstruments						4	4
Expected long-term rate of return on assets						7.25%
Subsequent Event
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, expected future employer contributions, remainder of fiscal year	$ 220,000,000
Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						$ 90,300,000	$ 92,300,000
Long Credit Bonds
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets						45.00%
Global Equities
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets						20.00%
Custom Completion
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets						10.00%
High Yield Bonds
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets						5.00%
Northern Trust Private Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets						5.00%
Northern Trust Private Equity Funds | Upper Limit
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets						20.00%
Emerging Market Debt
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets						4.00%
Global Listed Infrastructure
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets						4.00%
Real Estate
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets						4.00%
Northern Trust Hedge Fund
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets						3.00%
Supplemental Plan
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						$ 0	0
Prior service costs, amortization period (years)								10 years
Defined benefit plan, net periodic benefit cost (credit), gain (loss) due to settlement						0	0	$ 0
Actuarial Loss (Gain)						8,400,000	(20,000,000.0)
Prior service (benefit) cost						$ 0	$ 0	100,000
Weighted average discount rate used in determining the accumulated postretirement benefit obligation						4.95%	5.15%
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						$ 1,200,800,000	$ 1,176,800,000
Contributions made to the pension plan						$ 16,500,000	20,700,000
Fair value, investments, entities that calculate net asset value per share, investment redemption, notice period						60 days
Pension Plans, Defined Benefit | Lower Limit
Defined Benefit Plan Disclosure [Line Items]
Fair value, investments, entities that calculate net asset value per share, liquidating investment, remaining period						1 year
Pension Plans, Defined Benefit | Upper Limit
Defined Benefit Plan Disclosure [Line Items]
Fair value, investments, entities that calculate net asset value per share, liquidating investment, remaining period						15 years
Pension Plans, Defined Benefit | Northern Trust Private Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						$ 45,600,000	33,200,000
Pension Plans, Defined Benefit | Northern Trust Hedge Fund
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						36,200,000	35,200,000
Pension Plans, Defined Benefit | Domestic Common Stock
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						16,600,000	14,700,000
Pension Plans, Defined Benefit | Real Estate Funds
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						$ 82,900,000	99,100,000
Fair value, investments, entities that calculate net asset value per share, investment redemption, notice period						45 days
U.S. | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						$ 1,200,800,000	1,176,800,000	1,708,900,000
Contributions made to the pension plan						0	$ 0
Prior service costs, amortization period (years)							11 years
Defined benefit plan, net periodic benefit cost (credit), gain (loss) due to settlement						0	$ (44,100,000)	$ (27,900,000)
Actuarial Loss (Gain)						$ 36,800,000	(281,200,000)
Expected long-term rate of return on assets		6.00%	5.25%	6.50%	5.00%	7.25%		5.25%	5.25%
Prior service (benefit) cost						$ 0	$ (100,000)	$ (400,000)
Weighted average discount rate used in determining the accumulated postretirement benefit obligation						5.03%	5.22%
U.S. | Pension Plans, Defined Benefit | Subsequent Event
Defined Benefit Plan Disclosure [Line Items]
Contributions made to the pension plan	$ 200,000,000
U.S. | Pension Plans, Defined Benefit | Lower Limit
Defined Benefit Plan Disclosure [Line Items]
Contribution to plan assets						$ 0
U.S. | Pension Plans, Defined Benefit | Upper Limit
Defined Benefit Plan Disclosure [Line Items]
Contribution to plan assets						$ 420,000,000