Fair Value Measurements and Risk - Gain (Loss) on Derivative Instruments (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Gains and losses on derivative instruments
Interest and Debt Expense	$ (80.2)	$ (79.5)	$ (81.5)
Nonoperating Income (Expense)	16.5	(30.2)	(61.4)
Derivatives in ASC 815 cash flow hedging relationships
Gains and losses on derivative instruments
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	55.9	(5.6)	(3.3)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	46.6	(2.7)	(2.3)
Derivatives in ASC 815 cash flow hedging relationships | Cross Currency Interest Rate Contract [Member] | Interest Expense [Member]
Gains and losses on derivative instruments
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	9.7
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	(0.6)
Derivatives in ASC 815 cash flow hedging relationships | Cross Currency Interest Rate Contract [Member] | Nonoperating Income (Expense) [Member]
Gains and losses on derivative instruments
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	40.5
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	40.5
Derivatives in ASC 815 cash flow hedging relationships | Currency contracts
Gains and losses on derivative instruments
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	6.3	(3.6)	(0.1)
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	(0.4)	(0.6)
Derivatives in ASC 815 cash flow hedging relationships | Currency contracts | Nonoperating Income (Expense) [Member]
Gains and losses on derivative instruments
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	6.3	(2.9)	0.8
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	3.0	0.6
Derivatives in ASC 815 cash flow hedging relationships | Interest Rate Contract [Member]
Gains and losses on derivative instruments
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	0.4	0.9	(2.2)
Derivatives in ASC 815 cash flow hedging relationships | Interest Rate Contract [Member] | Interest Expense [Member]
Gains and losses on derivative instruments
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(0.6)	(2.7)	(4.1)
Not Designated as Hedging Instrument [Member] | Currency contracts | Nonoperating Income (Expense) [Member]
Gains and losses on derivative instruments
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ (4.0)	$ 1.0	$ (0.8)