Employee Benefits - Narrative (Detail)	12 Months Ended
	Dec. 31, 2025 USD ($) derivative	Dec. 31, 2024 USD ($) derivative	Dec. 31, 2023 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Actuarial (losses) gains	$ 20,600,000	$ 73,600,000
Number of derivatives held by the plan | derivative	5	5
Expected long-term rate of return on assets	7.25%
Defined contribution plan expense	$ 92,300,000	$ 78,800,000	$ 72,400,000
Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan	$ 86,300,000	83,300,000
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 | Maximum
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%
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan	$ 1,535,300,000	1,338,100,000
Contributions made to the pension plan	$ 12,900,000	8,000,000.0
Fair value, investments, entities that calculate net asset value per share, investment redemption, notice period	60 days
Pension Plans | Minimum
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 | Maximum
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	$ 62,200,000	53,200,000
Pension Plans | Northern Trust Hedge Fund
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan	41,500,000	39,200,000
Pension Plans | Domestic Common Stock
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan	62,700,000	17,600,000
Pension Plans | Real Estate Funds
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan	$ 66,400,000	73,000,000.0
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	$ 1,535,300,000	1,338,100,000	$ 1,200,800,000
Contributions made to the pension plan	125,000,000.0	200,000,000.0
Actuarial (losses) gains	$ 23,400,000	$ (60,900,000)
Expected long-term rate of return on assets	7.25%	7.25%	7.25%
U.S. | Pension Plans | Minimum
Defined Benefit Plan Disclosure [Line Items]
Contribution to plan assets	$ 0
U.S. | Pension Plans | Maximum
Defined Benefit Plan Disclosure [Line Items]
Contribution to plan assets	$ 280,000,000.0