Equity (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Changes in Accumulated Other Comprehensive Income (Loss)
January 1	$ (963.0)	$ (1,356.0)
Other comprehensive income (loss) before reclassifications	(212.3)	238.2
Reclassification from accumulated other comprehensive income (loss)	8.0	5.8
June 30	(1,167.3)	(1,112.0)
Cash Flow Hedge
Changes in Accumulated Other Comprehensive Income (Loss)
January 1	(26.3)	(29.5)
Other comprehensive income (loss) before reclassifications	0.0	0.0
Reclassification from accumulated other comprehensive income (loss)	2.0	1.6
June 30	(24.3)	(27.9)
Available-for-Sale Securities
Changes in Accumulated Other Comprehensive Income (Loss)
January 1	(0.3)	(0.8)
Other comprehensive income (loss) before reclassifications	0.0	0.3
Reclassification from accumulated other comprehensive income (loss)	0.3	0.0
June 30	0.0	(0.5)
Defined Benefit Pension Plans and Postemployment Arrangements
Changes in Accumulated Other Comprehensive Income (Loss)
January 1	(88.4)	(90.6)
Other comprehensive income (loss) before reclassifications	0.0	0.0
Reclassification from accumulated other comprehensive income (loss)	5.7	4.2
June 30	(82.7)	(86.4)
Foreign Currency Translation
Changes in Accumulated Other Comprehensive Income (Loss)
January 1	(848.0)	(1,235.1)
Other comprehensive income (loss) before reclassifications	(212.3)	237.9
Reclassification from accumulated other comprehensive income (loss)	0.0	0.0
June 30	$ (1,060.3)	$ (997.2)