Income Tax - Reconciliation of Statutory Federal Income Tax Rate (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory federal income tax rate		21.00%	21.00%	21.00%
Statutory federal income tax rate		$ 263.0	$ (13.1)	$ 260.2
State income taxes, net of federal benefits		2.40%	6.10%	4.70%
State income taxes, net of federal benefits		$ 30.6	$ (3.8)	$ 57.8
Effect of foreign tax rates		(2.40%)	92.60%	(5.50%)
Effect of foreign tax rates		$ (30.5)	$ (57.9)	$ (68.3)
Effect of foreign tax law and rate changes		0.90%	(0.80%)	1.60%
Effect of foreign tax law and rate changes		$ 11.5	$ 0.5	$ 19.6
Effect of unrecognized tax benefits		0.80%	(20.50%)	(6.20%)
Effect of unrecognized tax benefits	$ (73.0)	$ 9.5	$ 12.8	$ (76.3)
Change in valuation allowance		0.20%	1.10%	(0.10%)
Change in valuation allowance		$ 2.5	$ (0.7)	$ (1.1)
Goodwill impairment		0.00%	(287.00%)	(0.20%)
Goodwill impairment		$ 0.0	$ 179.3	$ (2.9)
Other, net		0.70%	(10.90%)	3.30%
Other, net		$ 9.5	$ 6.9	$ 41.5
Effective tax rate / Tax (benefit) expense		23.60%	(198.40%)	18.60%
Total income tax (benefit) expense		$ 296.1	$ 124.0	$ 230.5