Pension and Postretirement Benefits (Tables)

12 Months Ended

Dec. 31, 2023

Postemployment Benefits [Abstract]

Schedule of Changes in Benefit Obligations and Plan Assets

The following table sets forth the changes in our benefit obligations and plan assets for our pension and postretirement plans. The table also presents the line items in the consolidated balance sheet where the related assets and liabilities are recorded:

	Pension plans				Postretirement benefit obligations
	Year Ended December 31,				Year Ended December 31,
	2023		2022		2023		2022
Change in benefit obligation:
Benefit obligation at beginning of year	$	(1,400.4)	$	(1,832.4)	$	(1.0)	$	(1.3)
Service cost	(1.6)		(3.0)		—		—
Interest cost	(64.6)		(35.2)		—		—
Benefits paid	93.2		91.2		0.2		0.2
Plan amendment	0.5		0.2		—		—
Settlement	0.1		8.4		—		—
Plan participants' contributions	(0.9)		(0.9)		—		—
Actuarial (loss) gain	(28.9)		337.3		—		0.1
Effect of changes in foreign currency exchange rates	(14.9)		34.0		—		—
Benefit obligation at end of year	$	(1,417.5)	$	(1,400.4)	$	(0.8)	$	(1.0)
Change in plan assets:
Fair value of plan assets at beginning of year	$	1,250.2	$	1,696.4	$	—	$	—
Actual return on plan assets	106.2		(323.8)		—		—
Employer contributions	6.7		7.0		0.2		0.2
Plan participants' contributions	0.9		0.9		—		—
Benefits paid	(93.2)		(91.2)		(0.2)		(0.2)
Settlement	(0.1)		(8.4)		—		—
Effect of changes in foreign currency exchange rates	12.0		(30.7)		—		—
Fair value of plan assets at end of year	$	1,282.7	$	1,250.2	$	—	$	—
Net funded status of plan	$	(134.8)	$	(150.2)	$	(0.8)	$	(1.0)

	Pension plans				Postretirement benefit obligations
	December 31,				December 31,
	2023		2022		2023		2022
Amounts recorded in the consolidated balance sheets:
Prepaid pension assets (1)	$	5.6	$	4.0	$	—	$	—
Short-term pension and postretirement benefits (2)	(1.4)		(1.4)		(0.1)		(0.2)
Long-term pension and postretirement benefits (3)	(139.0)		(152.8)		(0.7)		(0.8)
Net amount recognized	$	(134.8)	$	(150.2)	$	(0.8)	$	(1.0)
Accumulated benefit obligation	$	1,410.9	$	1,393.4	N/A		N/A
Amount recognized in accumulated other comprehensive loss consists of:
Actuarial loss (gain)	$	82.3	$	76.3	$	(0.1)	$	(0.1)
Prior service cost (credit)	(0.6)		(0.1)		(1.3)		(1.7)
Total amount recognized - pretax	$	81.7	$	76.2	$	(1.4)	$	(1.8)

(1)Included within other non-current assets in the consolidated balance sheet.

(2)Included within accrued payroll in the consolidated balance sheet.

(3)Included within long-term pension and postretirement benefits in the consolidated balance sheet.

Schedule of Underfunded or Unfunded Accumulated Benefit Obligation and Related Projected Benefit Obligation

At December 31, 2023 and December 31, 2022, our underfunded or unfunded accumulated benefit obligation and the related projected benefit obligation were as follows:

	December 31,
	2023		2022
Accumulated benefit obligation	$	1,391.7	$	1,375.3
Fair value of plan assets	1,257.9		1,227.5
Unfunded accumulated benefit obligation	$	133.8	$	147.8
Projected benefit obligation	$	1,398.2	$	1,381.7

Schedule of Components of Net Periodic (Income) Cost Associated with Pension Plans and Postretirement Benefit Obligations

The following table sets forth the components of the net periodic cost (income) associated with our pension plans and our postretirement benefit obligations:

	Pension plans						Postretirement benefit obligations
	Year Ended December 31,						Year Ended December 31,
	2023		2022		2021		2023		2022		2021
Components of net periodic cost (income):
Service cost	$	1.6	$	3.0	$	5.2	$	—	$	—	$	—
Interest cost	64.6		35.2		27.4		—		—		—
Expected return on plan assets	(80.1)		(79.2)		(83.0)		—		—		—
Amortization of prior service cost (credit)	—		—		—		(0.4)		(0.4)		(0.4)
Amortization of actuarial loss (gain)	(2.4)		0.1		2.3		—		—		—
Net periodic cost (income)	$	(16.3)	$	(40.9)	$	(48.1)	$	(0.4)	$	(0.4)	$	(0.4)

Schedule of Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income

The following table sets forth other changes in plan assets and benefit obligations recognized in Other Comprehensive Income (Loss):

	Pension plans						Postretirement benefit obligations
	Year Ended December 31,						Year Ended December 31,
	2023		2022		2021		2023		2022		2021
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss)
Actuarial (loss) gain arising during the year, before tax benefit (expense) of $1.1, $15.6 and $(38.3) for the years ended December 31, 2023, 2022 and 2021, respectively.	$	(3.6)	$	(61.9)	$	145.1	$	—	$	0.2	$	0.1
Prior service credit (cost) arising during the year, before tax benefit (expense) of $(0.2), less than $0.1 and $(0.1) for the years ended December 31, 2023, 2022 and 2021, respectively	$	0.5	$	0.2	$	0.3	$	—	$	(0.1)	$	—
Less:
Amortization of actuarial (loss) gain, before tax benefit (expense) of $(0.7), less than $0.1 and $0.6 for the years ended December 31, 2023, 2022 and 2021, respectively.	$	2.4	$	(0.1)	$	(2.3)	$	—	$	—	$	—
Amortization of prior service (cost) credit, before tax benefit (expense) of $(0.1), $(0.1) and less than $(0.1) for the years ended December 31, 2023, 2022 and 2021, respectively.	$	—	$	—	$	—	$	0.4	$	0.4	$	0.4

Schedule of Weighted-Average Assumptions Used to Determine Projected Benefit Obligations and Periodic Benefit Cost

The following table sets forth the significant weighted-average assumptions we used to determine the projected benefit obligation and the periodic benefit cost:

	Pension plans						Postretirement benefit obligations
	Year Ended December 31,						Year Ended December 31,
	2023		2022		2021		2023		2022		2021
Discount rate for determining projected benefit obligation at December 31	4.57	%	4.83	%	2.38	%	4.81	%	4.70	%	1.80	%
Discount rate in effect for determining service cost	3.82	%	1.64	%	1.89	%	N/A		N/A		N/A
Discount rate in effect for determining interest cost	4.76	%	2.05	%	1.47	%	4.71	%	2.00	%	1.20	%
Weighted average expected long-term return on plan assets	5.60	%	5.32	%	5.70	%	N/A		N/A		N/A
Rate of compensation increase for determining projected benefit obligation at December 31	2.87	%	2.89	%	2.88	%	N/A		N/A		N/A
Rate of compensation increase for determining net pension cost	2.97	%	2.81	%	3.04	%	N/A		N/A		N/A
Interest credit rates for cash balance (1)	4.45% / 4.02%		4.45% / 3.94%		4.45% / 3.00%		N/A		N/A		N/A

(1)For our U.S. Qualified plan, interest for benefits accrued prior to January 1, 1997 is based on 30-year Treasury yield with a guaranteed minimum rate of 3.00% for accruals prior to January 1, 1997 and 4.45% for accruals after January 1, 1997. The resulting assumed interest rate for accruals prior to January 1, 1997 is 4.02% for December 31, 2023, 3.94% for December 31, 2022 and 3.00% for December 31, 2021. The resulting assumed interest rate for accruals after January 1, 1997 is 4.45%.

Schedule of Plan Assets at Fair Value

The following table sets forth by level, within the fair value hierarchy, the plan assets at fair value as of December 31, 2023:

Asset category	Quoted prices in active markets for identical assets (Level I)		Significant other observable inputs (Level II)		Significant unobservable inputs (Level III)		Total
Short-term investment funds	$	23.4	$	—	$	—	$	23.4
Aon Collective Investment Trust Funds:
Equity funds	$	222.3	$	—	$	—	$	222.3
Fixed income funds	622.7		—		—		622.7
Real estate funds	3.3		—		—		3.3
Total Aon Collective Investment Trust Funds	$	848.3	$	—	$	—	$	848.3
Total	$	871.7	$	—	$	—	$	871.7
Other Investments Measured at Net Asset Value
Aon Collective Investment Trust Funds							$	92.4
Aon Alternative Investment Funds:
Fixed income funds							$	76.3
Venture Capital Fund							6.6
Other Non-U.S. commingled equity and fixed income							235.7
Total other investments measured at net asset value							$	318.6
Total investments at fair value							$	1,282.7

The following table sets forth by level, within the fair value hierarchy, the plan assets at fair value as of December 31, 2022:

Asset category	Quoted prices in active markets for identical assets (Level I)		Significant other observable inputs (Level II)		Significant unobservable inputs (Level III)		Total
Short-term investment funds	$	9.1	$	—	$	—	$	9.1
Aon Collective Investment Trust Funds:
Equity funds	$	192.6	$	—	$	—	$	192.6
Fixed income funds	591.0		—		—		591.0
Real estate funds	3.0		—		—		3.0
Total Aon Collective Investment Trust Funds	$	786.6	$	—	$	—	$	786.6
Total	$	795.7	$	—	$	—	$	795.7
Other Investments Measured at Net Asset Value
Aon Collective Investment Trust Funds							$	123.4
Aon Alternative Investment Funds:
Fixed income funds							$	99.8
Venture Capital Fund							7.0
Other Non-U.S. commingled equity and fixed income							224.3
Total other investments measured at net asset value							$	331.1
Total investments at fair value							$	1,250.2

Schedule of Weighted Average Asset Allocations and Target Asset Allocations by Asset Category

The following table sets forth the weighted average asset allocations and target asset allocations by asset category, as of the measurement dates of the plans:

	Asset allocations				Target asset allocations
	December 31,				December 31,
	2023		2022		2023		2022
Return-seeking assets	36	%	43	%	37	%	37	%
Liability-hedging assets	64	%	57	%	63	%	63	%
Total	100	%	100	%	100	%	100	%

Schedule of Expected Benefit Payments

The following table summarizes expected benefit payments from our pension plans and postretirement plans through 2033. Actual benefit payments may differ from expected benefit payments. These amounts are net of expected plan participant contributions:

	Pension plans		Postretirement benefit plans
2024	$	96.0	$	0.2
2025	$	98.0	$	0.2
2026	$	99.4	$	0.1
2027	$	101.3	$	0.1
2028	$	102.5	$	0.1
2029 - 2033	$	506.9	$	0.1