Employee Benefits - Narrative (Detail)	1 Months Ended		3 Months Ended			12 Months Ended
	Jan. 31, 2025 USD ($)	Jan. 31, 2024 USD ($)	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Dec. 31, 2024 USD ($) derivative	Dec. 31, 2023 USD ($) derivative	Dec. 31, 2022 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Actuarial Loss (Gain)						$ (73,600,000)	$ 53,300,000
Number of derivatives held by the plan | derivative						4	4
Expected long-term rate of return on assets						7.25%
Defined contribution plan expense						$ 78,800,000	$ 72,400,000	$ 67,200,000
Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						$ 83,300,000	90,300,000
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
Defined benefit plan, net periodic benefit cost (credit), gain (loss) due to settlement						0	0	0
Actuarial Loss (Gain)						(800,000)	8,400,000
Prior service (benefit) cost						$ 0	$ 0	0
Weighted average discount rate used in determining the accumulated postretirement benefit obligation						5.55%	4.95%
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						$ 1,338,100,000	$ 1,200,800,000
Contributions made to the pension plan						$ 8,000,000.0	16,500,000
Fair value, investments, entities that calculate net asset value per share, investment redemption, notice period						60 days
Pension Plans | 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 | 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 | Northern Trust Private Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						$ 53,200,000	45,600,000
Pension Plans | Northern Trust Hedge Fund
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						39,200,000	36,200,000
Pension Plans | Domestic Common Stock
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						17,600,000	16,600,000
Pension Plans | Real Estate Funds
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						$ 73,000,000.0	82,900,000
Fair value, investments, entities that calculate net asset value per share, investment redemption, notice period						45 days
U.S. | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan						$ 1,338,100,000	1,200,800,000	1,176,800,000
Contributions made to the pension plan		$ 200,000,000.0				200,000,000.0	0
Defined benefit plan, net periodic benefit cost (credit), gain (loss) due to settlement						0	0	(44,100,000)
Actuarial Loss (Gain)						$ (60,900,000)	$ 36,800,000
Expected long-term rate of return on assets			6.50%	6.00%	5.25%	7.25%	7.25%
Prior service (benefit) cost						$ 0	$ 0	$ (100,000)
Weighted average discount rate used in determining the accumulated postretirement benefit obligation						5.70%	5.03%
U.S. | Pension Plans | Subsequent Event
Defined Benefit Plan Disclosure [Line Items]
Contributions made to the pension plan	$ 125,000,000.0
Defined benefit plan, expected future employer contributions, remainder of next fiscal year	$ 255,000,000.0
U.S. | Pension Plans | Lower Limit
Defined Benefit Plan Disclosure [Line Items]
Contribution to plan assets						$ 0
U.S. | Pension Plans | Upper Limit
Defined Benefit Plan Disclosure [Line Items]
Contribution to plan assets						$ 380,000,000.0