Retirement Benefits - Projected Benefit Obligation Assumptions (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	5.16%	5.46%	2.79%
Rate of compensation increase	0.08%	0.08%	0.08%
Discount rate	5.46%	2.79%	2.47%
Expected return on plan assets	5.68%	4.59%	4.66%
Rate of compensation increase	0.08%	0.08%	0.24%
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	5.20%	5.50%	2.90%
Rate of compensation increase	5.00%	3.93%	3.87%
Discount rate	5.50%	2.90%	2.50%
Rate of compensation increase	3.93%	3.87%	3.99%