Income Taxes (Earnings (Loss) Before Income Tax) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Examination [Line Items]
Earnings (loss) from continuing operations before income taxes	$ (1,156.0)	$ 161.8	$ (2,111.1)
Discontinued Operations
Income Tax Examination [Line Items]
Earnings (loss) from continuing operations before income taxes	(237.2)	(426.4)	(499.9)
Continuing Operations | Domestic tax authority | U.K.
Income Tax Examination [Line Items]
Earnings (loss) from continuing operations before income taxes	(831.0)	330.9	(991.3)
Continuing Operations | Foreign tax authority | The Netherlands
Income Tax Examination [Line Items]
Earnings (loss) from continuing operations before income taxes	(662.8)	(321.1)	(26.1)
Continuing Operations | Foreign tax authority | Belgium
Income Tax Examination [Line Items]
Earnings (loss) from continuing operations before income taxes	409.3	392.4	140.0
Continuing Operations | Foreign tax authority | Switzerland
Income Tax Examination [Line Items]
Earnings (loss) from continuing operations before income taxes	178.5	318.8	111.6
Continuing Operations | Foreign tax authority | U.S.
Income Tax Examination [Line Items]
Earnings (loss) from continuing operations before income taxes	(7.0)	(51.6)	(842.5)
Continuing Operations | Foreign tax authority | Other
Income Tax Examination [Line Items]
Earnings (loss) from continuing operations before income taxes	$ (5.8)	$ (81.2)	$ (2.9)