Derivative Financial Instruments (Changes in AOCI Relating to Derivatives) (Details) - Qualifying Hedges - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives - effective portion reclassified from AOCI to income	$ 0.0	$ 0.0	$ 13.4	$ 1.8
Hedge ineffectiveness recorded directly in income	0.0	0.0	0.0	0.0
Total income statement impact	0.0	0.0	13.4	1.8
Derivatives - effective portion recorded in OCI	(33.0)	4.2	(74.7)	(28.1)
Total change in OCI for period	(33.0)	4.2	(88.1)	(29.9)
Foreign currency forward contracts | Foreign currency forward contracts — net investment hedges
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives - effective portion reclassified from AOCI to income	0.0	0.0	13.4	1.8
Hedge ineffectiveness recorded directly in income	0.0	0.0	0.0	0.0
Total income statement impact	0.0	0.0	13.4	1.8
Derivatives - effective portion recorded in OCI	(33.0)	4.2	(74.7)	(28.1)
Total change in OCI for period	$ (33.0)	$ 4.2	$ (88.1)	$ (29.9)