Accumulated Other Comprehensive Loss, Net of Tax (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Foreign currency translation adjustment:
Balance at beginning of period	$ (716.4)	$ (585.3)
Other comprehensive (loss) income before reclassifications	(37.2)	(119.6)
Amount reclassified from accumulated other comprehensive loss, net of tax	5.2	16.7
Balance at end of period	(748.4)	(688.2)
Derivative Instrument:
Balance at beginning of period	(3.9)	(5.6)	$ (5.3)	$ (6.8)
Other comprehensive (loss) income before reclassifications, related to Derivative Instruments	0.0	0.0
Amount reclassified from accumulated other comprehensive loss, net of tax, related to Derivative Instruments	1.4	1.2
Defined Benefit Pension and Other Postretirement Plans
Balance at beginning of period	(219.4)	(235.7)
Other comprehensive (loss) income before reclassifications	1.6	(0.6)
Amount reclassified from accumulated other comprehensive loss, net of tax	3.9	4.8
Balance at end of period	(213.9)	(231.5)
Total:
Balance at beginning of period	(941.1)	(827.8)
Other comprehensive (loss) income before reclassifications	(35.6)	(120.2)
Amount reclassified from accumulated other comprehensive loss, net of tax	10.5	22.7
Balance at end of period	$ (966.2)	$ (925.3)