Summary of Significant Accounting Policies - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ 6,612.9
Other Comprehensive Income (Loss) before Reclassifications, Tax [Abstract]
Increase (decrease)		20.7	$ (127.0)	$ 133.1
Income tax impact		7.3	(0.2)	0.9
Other comprehensive income (loss) before reclassifications, net of income taxes		28.0	(127.2)	134.0
Reclassification from AOCI, Current Period, Tax [Abstract]
Increase (decrease)		3.1	4.3	5.5
Income tax impact		(0.8)	(0.8)	(1.3)
Amounts reclassified from accumulated other comprehensive income (loss), net of income taxes		2.3	3.5	4.2
Total other comprehensive income (loss), net of income taxes		30.3	(123.7)	138.2
Divestiture of A&S Business			44.7
Ending balance		7,400.2	6,612.9
Foreign currency translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(29.3)	64.0	(72.6)
Other Comprehensive Income (Loss) before Reclassifications, Tax [Abstract]
Increase (decrease)		50.5	(127.3)	136.6
Income tax impact		0.0	0.0	0.0
Other comprehensive income (loss) before reclassifications, net of income taxes		50.5	(127.3)	136.6
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		50.5	(127.3)	136.6
Divestiture of A&S Business			34.0
Ending balance		21.2	(29.3)	64.0
Pension & post-retirement plan benefit adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[1]	(57.3)	(71.6)	(73.2)
Other Comprehensive Income (Loss) before Reclassifications, Tax [Abstract]
Increase (decrease)	[1]	(29.8)	0.3	(3.5)
Income tax impact	[1]	7.3	(0.2)	0.9
Other comprehensive income (loss) before reclassifications, net of income taxes	[1]	(22.5)	0.1	(2.6)
Reclassification from AOCI, Current Period, Tax [Abstract]
Increase (decrease)	[1],[2]	3.1	4.3	5.5
Income tax impact	[1]	(0.8)	(0.8)	(1.3)
Amounts reclassified from accumulated other comprehensive income (loss), net of income taxes	[1]	2.3	3.5	4.2
Total other comprehensive income (loss), net of income taxes	[1]	(20.2)	3.6	1.6
Divestiture of A&S Business	[1]		10.7
Ending balance	[1]	(77.5)	(57.3)	(71.6)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(86.6)	(7.6)	(145.8)
Reclassification from AOCI, Current Period, Tax [Abstract]
Total other comprehensive income (loss), net of income taxes		30.3	(123.7)	138.2
Divestiture of A&S Business			44.7
Ending balance		$ (56.3)	$ (86.6)	$ (7.6)

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

[2] This component of AOCI is included in the computation of net periodic pension cost (refer to Note 12 for additional details) and also includes activity related to the divestiture of the A&S Business.