Retirement Benefits - Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
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	$ 139.0	$ 178.0	$ 168.0
% 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	$ 0.2	$ 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	18.00%	18.00%
% Target Allocation	22.00%	19.00%
UMWA Plans | U.S. large-cap(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 25.6	$ 32.8
UMWA Plans | U.S. small/mid-cap(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	7.00%	8.00%
% Target Allocation	10.00%	8.00%
UMWA Plans | U.S. small/mid-cap(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 10.0	$ 13.8
UMWA Plans | International(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	20.00%	23.00%
% Target Allocation	24.00%	24.00%
UMWA Plans | International(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 28.2	$ 40.4
UMWA Plans | Emerging markets(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	4.00%	4.00%
% Target Allocation	4.00%	4.00%
UMWA Plans | Emerging markets(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 4.9	$ 6.7
UMWA Plans | Dynamic asset allocation(c)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	6.00%	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	$ 8.5	$ 12.1
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	$ 3.5
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	$ 5.0	$ 6.7
UMWA Plans | Multi asset real return(i)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	4.00%	5.00%
% Target Allocation	5.00%	5.00%
UMWA Plans | Multi asset real return(i) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 6.1	$ 8.6
UMWA Plans | Core property(g) (l)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	15.00%	9.00%
% Target Allocation	10.00%	10.00%
UMWA Plans | Core property(g) (l) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 20.6	$ 16.6
UMWA Plans | Structured credit(h) (l)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	9.00%	7.00%
% Target Allocation	5.00%	5.00%
UMWA Plans | Structured credit(h) (l) | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 12.8	$ 13.1
UMWA Plans | Global private equity(j) (l)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 11.9	$ 13.9
% Actual Allocation	9.00%	8.00%
% Target Allocation	7.00%	7.00%
UMWA Plans | Energy debt(k) (l)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 2.8	$ 9.8
% Actual Allocation	2.00%	5.00%
% Target Allocation	0.00%	5.00%
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	$ 596.3	$ 764.8	747.1
% 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	$ 3.9
% 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	15.00%	20.00%
% Target Allocation	16.00%	20.00%
U.S. Plans | U.S. large-cap(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 90.2	$ 150.4
U.S. Plans | U.S. small/mid-cap(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	5.00%	7.00%
% Target Allocation	5.00%	7.00%
U.S. Plans | U.S. small/mid-cap(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 27.9	$ 52.4
U.S. Plans | International(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	17.00%	21.00%
% Target Allocation	17.00%	22.00%
U.S. Plans | International(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 99.2	$ 162.5
U.S. Plans | Emerging markets(a)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	2.00%	4.00%
% Target Allocation	2.00%	4.00%
U.S. Plans | Emerging markets(a) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 11.5	$ 29.0
U.S. Plans | Dynamic asset allocation(c)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	5.00%	7.00%
% Target Allocation	5.00%	7.00%
U.S. Plans | Dynamic asset allocation(c) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 28.1	$ 52.5
U.S. Plans | Long duration - mutual fund(d)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	44.00%	29.00%
% Target Allocation	45.00%	30.00%
U.S. Plans | Long duration - mutual fund(d) | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 189.4	$ 186.7
U.S. Plans | Long duration - Treasury strips(d) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 74.9	$ 38.3
U.S. Plans | Core property(g) (l)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	6.00%	6.00%
% Target Allocation	5.00%	5.00%
U.S. Plans | Core property(g) (l) | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 36.2	$ 43.7
U.S. Plans | Structured credit(h) (l)
Defined Benefit Plan Disclosure [Line Items]
% Actual Allocation	6.00%	6.00%
% Target Allocation	5.00%	5.00%
U.S. Plans | Structured credit(h) (l) | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 35.1	$ 45.4
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 245.5	$ 360.3	$ 355.8
% 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	$ 0.7	$ 0.8
% 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	$ 30.0	$ 75.4
% Actual Allocation	12.00%	21.00%
% Target Allocation	13.00%	18.00%
Non-U.S. Plans | U.S. equity funds(a)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 9.6	$ 22.8
Non-U.S. Plans | Canadian equity funds(a)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	3.6	9.6
Non-U.S. Plans | European equity funds(a)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	1.4	4.5
Non-U.S. Plans | Other global equity funds(a)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	15.4	38.5
Non-U.S. Plans | Fixed-income securities:
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 113.9	$ 149.3
% Actual Allocation	47.00%	42.00%
% Target Allocation	47.00%	44.00%
Non-U.S. Plans | Long duration - mutual fund(d)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 59.5	$ 63.9
Non-U.S. Plans | High yield(e)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	0.7	2.0
Non-U.S. Plans | Emerging markets(f)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	0.7	2.1
Non-U.S. Plans | Canadian fixed-income securities(b)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	42.0	71.5
Non-U.S. Plans | European fixed-income funds(c)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	11.0	9.8
Non-U.S. Plans | Other types of investments:
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 100.9	$ 134.8
% Actual Allocation	10.00%	7.00%
% Target Allocation	7.00%	6.00%
Non-U.S. Plans | Guaranteed contract value
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 75.8	$ 109.7
% Actual Allocation	31.00%	30.00%
% Target Allocation	33.00%	32.00%
Non-U.S. Plans | Property funds(h)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 9.6	$ 9.4
Non-U.S. Plans | Global infrastructure fund(i)
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	6.8	9.7
Non-U.S. Plans | Other
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value	$ 8.7	$ 6.0