Taxation (Operating Loss and Tax Credit Carryforwards, and Their Expiration Dates) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 1,907.3	$ 980.3
Expirations of Tax Benefit Carryforwards
Within 1 year	0.3
Within 1 to 2 years	2.6
Within 2 to 3 years	45.5
Within 3 to 4 years	12.8
Within 4 to 5 years	52.6
Within 5 to 6 years	55.3
After 6 years	1,269.6
Indefinitely	468.6
U.S. federal tax
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	687.1	149.3
US state
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	170.7	77.2
Republic of Ireland
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	45.1	61.2
Foreign tax jurisdictions
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	614.9	434.9
R&D and other tax credits
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 389.5	$ 257.7