Summary of Significant Accounting Policies - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), beginning of period		$ 3,808.2
Reclassification from AOCI, Current Period, Tax [Abstract]
Total other comprehensive income (loss), net of income taxes		(123.7)	$ 138.2	$ (131.4)
Accumulated other comprehensive income (loss), beginning of period		6,612.9	3,808.2
Foreign currency translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), beginning of period		64.0	(72.6)	51.2
Other Comprehensive Income (Loss) before Reclassifications, Tax [Abstract]
Increase (decrease)		(127.3)	136.6	(123.8)
Income tax impact		0.0	0.0	0.0
Other comprehensive income (loss) before reclassifications, net of income taxes		(127.3)	136.6	(123.8)
Reclassification from AOCI, Current Period, Tax [Abstract]
Increase (decrease)		0.0	0.0	0.0
Income tax impact		0.0	0.0	0.0
Amounts reclassified from accumulated other comprehensive income (loss), net of income taxes		0.0	0.0	0.0
Total other comprehensive income (loss), net of income taxes		(127.3)	136.6	(123.8)
Split-off of A&S Business		34.0
Accumulated other comprehensive income (loss), beginning of period		(29.3)	64.0	(72.6)
Pension & post- retirement plan benefit adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), beginning of period	[1]	(71.6)	(73.2)	(65.6)
Other Comprehensive Income (Loss) before Reclassifications, Tax [Abstract]
Increase (decrease)	[1]	0.3	(3.5)	(13.8)
Income tax impact	[1]	(0.2)	0.9	2.0
Other comprehensive income (loss) before reclassifications, net of income taxes	[1]	0.1	(2.6)	(11.8)
Reclassification from AOCI, Current Period, Tax [Abstract]
Increase (decrease)	[1],[2]	4.3	5.5	5.5
Income tax impact	[1]	(0.8)	(1.3)	(1.3)
Amounts reclassified from accumulated other comprehensive income (loss), net of income taxes	[1]	3.5	4.2	4.2
Total other comprehensive income (loss), net of income taxes	[1]	3.6	1.6	(7.6)
Split-off of A&S Business	[1]	10.7
Accumulated other comprehensive income (loss), beginning of period	[1]	(57.3)	(71.6)	(73.2)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), beginning of period		(7.6)	(145.8)	(14.4)
Other Comprehensive Income (Loss) before Reclassifications, Tax [Abstract]
Increase (decrease)		(127.0)	133.1	(137.6)
Income tax impact		(0.2)	0.9	2.0
Other comprehensive income (loss) before reclassifications, net of income taxes		(127.2)	134.0	(135.6)
Reclassification from AOCI, Current Period, Tax [Abstract]
Increase (decrease)		4.3	5.5	5.5
Income tax impact		(0.8)	(1.3)	(1.3)
Amounts reclassified from accumulated other comprehensive income (loss), net of income taxes		3.5	4.2	4.2
Total other comprehensive income (loss), net of income taxes		(123.7)	138.2	(131.4)
Split-off of A&S Business		44.7
Accumulated other comprehensive income (loss), beginning of period		$ (86.6)	$ (7.6)	$ (145.8)

[1] Includes balances relating to employee defined benefit plans, supplemental executive retirement plans and other postretirement employee benefit plans.

[2] This accumulated other comprehensive income (loss) component is included in the computation of net periodic pension cost (refer to Note 11 for additional details) and also includes activity related to the divestiture of the A&S Business.