Retirement Benefits - Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Maximum average weighted maturity (in years)	10 years
UMWA Plans
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 129.5	$ 136.1	$ 139.0
% Actual Allocation	100.00%	100.00%
% Target Allocation	100.00%	100.00%
UMWA Plans | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 0.0	$ 0.0
% Actual Allocation	0.00%	0.00%
% Target Allocation	0.00%	0.00%
UMWA Plans | U.S. large-cap(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	23.00%	22.00%
% Target Allocation	24.00%	24.00%
UMWA Plans | U.S. large-cap(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 29.3	$ 29.3
UMWA Plans | U.S. small/mid-cap(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	10.00%	10.00%
% Target Allocation	11.00%	11.00%
UMWA Plans | U.S. small/mid-cap(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 13.3	$ 13.2
UMWA Plans | International(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	24.00%	24.00%
% Target Allocation	26.00%	26.00%
UMWA Plans | International(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 30.7	$ 32.1
UMWA Plans | Emerging markets(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	3.00%	3.00%
% Target Allocation	4.00%	4.00%
UMWA Plans | Emerging markets(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 4.8	$ 5.1
UMWA Plans | Dynamic asset allocation(c)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	7.00%	7.00%
% Target Allocation	7.00%	7.00%
UMWA Plans | Dynamic asset allocation(c) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 8.6	$ 8.9
UMWA Plans | High yield(e)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	2.00%	2.00%
% Target Allocation	2.00%	2.00%
UMWA Plans | High yield(e) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 2.4	$ 2.6
UMWA Plans | Emerging markets(f)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	4.00%	4.00%
% Target Allocation	4.00%	4.00%
UMWA Plans | Emerging markets(f) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 4.8	$ 5.1
UMWA Plans | Multi asset real return(i)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	4.00%	4.00%
% Target Allocation	5.00%	5.00%
UMWA Plans | Multi asset real return(i) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 6.0	$ 6.1
UMWA Plans | Core property(g) (l)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	8.00%	10.00%
% Target Allocation	5.00%	5.00%
UMWA Plans | Core property(g) (l) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 10.6	$ 14.7
UMWA Plans | Structured credit
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	8.00%	6.00%
% Target Allocation	5.00%	5.00%
UMWA Plans | Structured credit | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 10.0	$ 8.3
UMWA Plans | Global private equity(j) (l)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 8.2	$ 9.6
% Actual Allocation	6.00%	7.00%
% Target Allocation	7.00%	7.00%
UMWA Plans | Energy debt
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 0.8	$ 1.1
% Actual Allocation	1.00%	1.00%
% Target Allocation	0.00%	0.00%
Minimum
Defined Benefit Plan Disclosure [Line Items]
Maximum average weighted maturity (in years)	5 years
Minimum | Long duration - mutual fund(d)
Defined Benefit Plan Disclosure [Line Items]
Portfolio duration (in years)	10 years
Maximum
Defined Benefit Plan Disclosure [Line Items]
Maximum average weighted maturity (in years)	7 years
Maximum | Long duration - mutual fund(d)
Defined Benefit Plan Disclosure [Line Items]
Portfolio duration (in years)	15 years
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 587.7	$ 611.6	596.3
% Actual Allocation	100.00%	100.00%
% Target Allocation	100.00%	100.00%
U.S. Plans | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 3.8	$ 3.8
% Actual Allocation	0.00%	0.00%
% Target Allocation	0.00%	0.00%
U.S. Plans | U.S. large-cap(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	13.00%	9.00%
% Target Allocation	14.00%	13.00%
U.S. Plans | U.S. large-cap(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 75.2	$ 57.6
U.S. Plans | U.S. small/mid-cap(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	4.00%	3.00%
% Target Allocation	4.00%	4.00%
U.S. Plans | U.S. small/mid-cap(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 20.9	$ 15.4
U.S. Plans | International(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	11.00%	10.00%
% Target Allocation	12.00%	14.00%
U.S. Plans | International(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 66.7	$ 63.7
U.S. Plans | Emerging markets(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	0.00%	1.00%
% Target Allocation	0.00%	1.00%
U.S. Plans | Emerging markets(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 0.0	$ 4.5
U.S. Plans | Dynamic asset allocation(c)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	0.00%	3.00%
% Target Allocation	0.00%	3.00%
U.S. Plans | Dynamic asset allocation(c) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 0.0	$ 15.6
U.S. Plans | Long duration - mutual fund(d)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	68.00%	62.00%
% Target Allocation	70.00%	60.00%
U.S. Plans | Long duration - mutual fund(d) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 343.8	$ 317.4
U.S. Plans | Long duration - Treasury strips(d) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 55.3	$ 58.9
U.S. Plans | Core property(g) (l)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	4.00%	5.00%
% Target Allocation	0.00%	2.00%
U.S. Plans | Core property(g) (l) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 21.3	$ 33.0
U.S. Plans | Structured credit
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	0.00%	7.00%
% Target Allocation	0.00%	3.00%
U.S. Plans | Structured credit | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 0.7	$ 41.7
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 238.5	$ 259.3	$ 245.5
% Actual Allocation	100.00%	100.00%
% Target Allocation	100.00%	100.00%
Non-U.S. Plans | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 0.5	$ 0.9
% Actual Allocation	0.00%	0.00%
% Target Allocation	0.00%	0.00%
Non-U.S. Plans | Equity securities:
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 17.8	$ 20.0
% Actual Allocation	7.00%	8.00%
% Target Allocation	9.00%	10.00%
Non-U.S. Plans | U.S. equity funds(a)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 7.3	$ 7.4
Non-U.S. Plans | Canadian equity funds(a)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	1.8	1.6
Non-U.S. Plans | European equity funds(a)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	0.6	1.4
Non-U.S. Plans | Other global equity funds(a)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	8.1	9.6
Non-U.S. Plans | Fixed-income securities:
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 121.2	$ 130.0
% Actual Allocation	51.00%	50.00%
% Target Allocation	49.00%	49.00%
Non-U.S. Plans | Long duration - mutual fund(d)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 57.5	$ 61.4
Non-U.S. Plans | High yield(e)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	0.3	0.7
Non-U.S. Plans | Emerging markets(f)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	0.3	0.8
Non-U.S. Plans | Canadian fixed-income securities(b)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	49.7	55.4
Non-U.S. Plans | European fixed-income funds(c)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	13.4	11.7
Non-U.S. Plans | Other types of investments:
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 99.0	$ 108.4
% Actual Allocation	9.00%	10.00%
% Target Allocation	7.00%	7.00%
Non-U.S. Plans | Guaranteed contract value
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 77.9	$ 82.6
% Actual Allocation	33.00%	32.00%
% Target Allocation	35.00%	34.00%
Non-U.S. Plans | Property funds(h)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 6.2	$ 11.1
Non-U.S. Plans | Global infrastructure fund(i)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	7.5	7.5
Non-U.S. Plans | Other
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 7.4	$ 7.2