Income Taxes (Benefit (Expense) of Income Tax) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Line Items]
Current	$ (182.7)	$ (146.4)	$ (155.1)
Deferred	33.1	(172.5)	(318.2)
Total income tax expense	(149.6)	(318.9)	(473.3)
Belgium
Income Taxes [Line Items]
Current	(100.9)	(87.7)	(96.3)
Deferred	(64.9)	17.1	16.2
Total	(165.8)	(70.6)	(80.1)
U.S.
Income Taxes [Line Items]
Current	(68.0)	(51.8)	(47.9)
Deferred	(28.4)	(133.0)	(25.8)
Total	(96.4)	(184.8)	(73.7)
Switzerland
Income Taxes [Line Items]
Current	(0.3)	0.6	(7.2)
Deferred	78.9	87.2	63.5
Total	78.6	87.8	56.3
Luxembourg
Income Taxes [Line Items]
Current	0.0	(0.3)	(0.4)
Deferred	44.3	(152.3)	(49.5)
Total	44.3	(152.6)	(49.9)
The Netherlands
Income Taxes [Line Items]
Current	(16.9)	(1.7)	(2.6)
Deferred	0.2	(0.8)	(1.3)
Total	(16.7)	(2.5)	(3.9)
Ireland
Income Taxes [Line Items]
Current	3.6	(5.3)	(0.7)
Deferred	2.5	10.5	0.0
Total	6.1	5.2	(0.7)
U.K.
Income Taxes [Line Items]
Current	(0.1)	(0.1)	(0.4)
Deferred	0.5	0.8	(319.5)
Total	0.4	0.7	(319.9)
Other
Income Taxes [Line Items]
Current	(0.1)	(0.1)	0.4
Deferred	0.0	(2.0)	(1.8)
Total	$ (0.1)	$ (2.1)	$ (1.4)