Equity Investments (Summary of Investment in Joint Venture, Balance Sheet Data) (Details) - WAVE [Member] - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Current assets	$ 99.2	$ 112.9
Current assets of discontinued operations		33.8
Noncurrent assets	37.0	34.9
Current liabilities	24.4	113.6
Current liabilities of discontinued operations		6.9
Other noncurrent liabilities	$ 287.4	$ 293.6