Revenue and Contracts with Customers (Revenue from External Customers by Geographic Areas) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Revenue		$ 247.2	$ 209.7
United States
Revenue		171.7	152.4
Belgium
Revenue	$ 35.8		21.5
Japan
Revenue		23.4	23.4
Other Foreign
Revenue		16.3	12.4
Foreign
Revenue		75.5	57.3
Product [Member]
Revenue		190.5	169.4
Product [Member] | United States
Revenue		115.0	112.1
Product [Member] | Belgium
Revenue		35.8	21.5
Product [Member] | Japan
Revenue		23.4
Product [Member] | Other Foreign
Revenue		16.3	12.4
Product [Member] | Foreign
Revenue		$ 75.5	$ 57.3