Description of the Business and Significant Accounting Policies (Cash and Equivalents And Restricted Cash) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Restricted Cash and Cash Equivalents	$ 5.8	$ 6.2	$ 5.6	$ 6.4
Restricted Cash and Cash Equivalents, Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent