Retirement Benefits - Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Contribution Plan Disclosure [Line Items]
Matching defined contribution expense	$ 20.6	$ 19.1	$ 19.1
Defined contribution plan maximum annual contribution per employee percent	2.00%
U.S. 401(K)
Defined Contribution Plan Disclosure [Line Items]
Matching defined contribution expense	$ 9.9	7.6	6.5
Other plans
Defined Contribution Plan Disclosure [Line Items]
Matching defined contribution expense	$ 10.7	$ 11.5	$ 12.6