Taxation (Pretax Income from Continuing Operations and Provision for Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Total current taxes	$ 566.6	$ 422.9	$ 227.6
Total deferred taxes	(2,924.2)	(549.0)	(181.5)
Total income taxes	(2,357.6)	(126.1)	46.1
Ireland
Income Tax Contingency [Line Items]
Current domestic tax expense	46.6	5.2	0.8
Deferred domestic tax expense (benefit)	22.3	18.2	(38.8)
U.S. federal tax
Income Tax Contingency [Line Items]
Current foreign tax expense	373.8	318.6	191.7
Deferred foreign tax expense (benefit)	(3,050.3)	(433.8)	(151.2)
U.S. state tax
Income Tax Contingency [Line Items]
Current foreign tax expense	55.8	30.2	17.3
Deferred foreign tax expense (benefit)	260.1	(74.1)	(1.7)
Foreign tax jurisdictions
Income Tax Contingency [Line Items]
Current rest of the world tax expense	90.4	68.9	17.8
Deferred rest of the world tax expense (benefit)	$ (156.3)	$ (59.3)	$ 10.2