Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period	$ 2,395.2
Balance at the end of the period	2,465.4
Foreign Currency Translation
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period	(134.0)	$ (230.0)
Other comprehensive income before reclassifications	30.7	24.3
Net current period other comprehensive income	30.7	24.3
Balance at the end of the period	(103.3)	(205.7)
Other
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period	(12.5)	(20.7)
Other comprehensive income before reclassifications	1.1	1.4
Net current period other comprehensive income	1.1	1.4
Balance at the end of the period	(11.4)	(19.3)
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period	(146.5)	(250.7)
Other comprehensive income before reclassifications	31.8	25.7
Net current period other comprehensive income	31.8	25.7
Balance at the end of the period	$ (114.7)	$ (225.0)