Equity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
January 1	$ (963.0)	$ (1,356.0)
Other comprehensive income (loss) before reclassifications	83.7	100.0
Reclassification from accumulated other comprehensive income (loss)	4.2	2.9
March 31	(875.1)	(1,253.1)
Cash Flow Hedge
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
January 1	(26.3)	(29.5)
Other comprehensive income (loss) before reclassifications	0.0	0.0
Reclassification from accumulated other comprehensive income (loss)	1.0	0.8
March 31	(25.3)	(28.7)
Available-for-Sale Securities
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
January 1	(0.3)	(0.8)
Other comprehensive income (loss) before reclassifications	0.0	0.1
Reclassification from accumulated other comprehensive income (loss)	0.3	0.0
March 31	0.0	(0.7)
Defined Benefit Pension Plans and Postemployment Arrangements
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
January 1	(88.4)	(90.6)
Other comprehensive income (loss) before reclassifications	0.0	0.0
Reclassification from accumulated other comprehensive income (loss)	2.9	2.1
March 31	(85.5)	(88.5)
Foreign Currency Translation
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
January 1	(848.0)	(1,235.1)
Other comprehensive income (loss) before reclassifications	83.7	99.9
Reclassification from accumulated other comprehensive income (loss)	0.0	0.0
March 31	$ (764.3)	$ (1,135.2)