Income Taxes (Details 5) $ in Millions	Dec. 31, 2018 USD ($)
Operating Loss Carryforwards [Line Items]
Tax loss carryforward	$ 23,544.8
Related tax asset	4,289.8
U.K.
Operating Loss Carryforwards [Line Items]
Tax loss carryforward	1,025.6
Related tax asset	174.3
U.K. | Amount attributable to capital losses
Operating Loss Carryforwards [Line Items]
Tax loss carryforward	15,426.3
Related tax asset	2,622.5
The Netherlands
Operating Loss Carryforwards [Line Items]
Tax loss carryforward	3,923.1
Related tax asset	842.5
Belgium
Operating Loss Carryforwards [Line Items]
Tax loss carryforward	1,288.9
Related tax asset	324.1
Ireland
Operating Loss Carryforwards [Line Items]
Tax loss carryforward	708.5
Related tax asset	88.8
France
Operating Loss Carryforwards [Line Items]
Tax loss carryforward	544.5
Related tax asset	157.5
U.S.
Operating Loss Carryforwards [Line Items]
Tax loss carryforward	382.3
Related tax asset	16.8
Other
Operating Loss Carryforwards [Line Items]
Tax loss carryforward	245.6
Related tax asset	$ 63.3