Equity Investment (Summary of the Difference Between Carrying Amount and Underlying Equity of Equity Method Investment) (Details) - WAVE [Member] - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Total of fair value adjustments to assets	$ 145.8	$ 155.5
Property, Plant and Equipment [Member]
Schedule of Equity Method Investments [Line Items]
Total of fair value adjustments to assets	0.4	0.4
Other Intangibles [Member]
Schedule of Equity Method Investments [Line Items]
Total of fair value adjustments to assets	115.0	124.7
Goodwill [Member]
Schedule of Equity Method Investments [Line Items]
Total of fair value adjustments to assets	$ 30.4	$ 30.4