Income Taxes (Benefit (Expense) of Income Tax) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Current	$ 13.0	$ (155.1)		$ (169.5)
Deferred	262.9	(318.2)	$ 262.9	(64.5)
Income tax benefit (expense)	275.9	(473.3)	$ 275.9	(234.0)
U.K.
Income Taxes [Line Items]
Current	(1.3)	(0.4)		(1.5)
Deferred	52.2	(319.5)		118.8
Total	50.9	(319.9)		117.3
U.S.
Income Taxes [Line Items]
Current	81.5	(47.9)		(4.1)
Deferred	159.7	(25.8)		81.9
Total	241.2	(73.7)		77.8
Belgium
Income Taxes [Line Items]
Current	(54.5)	(96.3)		(134.7)
Deferred	36.3	16.2		3.6
Total	(18.2)	(80.1)		(131.1)
Switzerland
Income Taxes [Line Items]
Current	(3.5)	(7.2)		(27.8)
Deferred	41.2	63.5		(1.1)
Total	37.7	56.3		(28.9)
Luxembourg
Income Taxes [Line Items]
Current	(0.3)	(0.4)		(1.2)
Deferred	(27.1)	(49.5)		7.7
Total	(27.4)	(49.9)		6.5
The Netherlands
Income Taxes [Line Items]
Current	(7.7)	(2.6)		0.0
Deferred	0.0	(1.3)		(275.3)
Total	(7.7)	(3.9)		(275.3)
Other
Income Taxes [Line Items]
Current	(1.2)	(0.3)		(0.2)
Deferred	0.6	(1.8)		(0.1)
Total	$ (0.6)	$ (2.1)		$ (0.3)