Inventories (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Inventory [Line Items]
Raw materials and supplies	$ 202.2		$ 202.2		$ 164.9
Work-in-process	796.8		796.8		899.6
Finished goods	186.5		186.5		161.3
Total inventories at current cost	1,185.5		1,185.5		1,225.8
Adjustment from current cost to LIFO cost basis	47.6		47.6		33.6
Inventory valuation reserves	(129.6)		(129.6)		(104.1)
Total inventories, net	1,103.5		1,103.5		1,155.3
LIFO benefit			14.0	$ 5.8
NRV charge			(14.0)	(5.9)
Net cost of sales impact	0.0	$ 0.0	0.0	$ (0.1)
Net Realizable Value Reserve [Member]
Inventory [Line Items]
Inventory valuation reserves	$ (47.6)		$ (47.6)		$ (33.6)