Description of the Business and Significant Accounting Policies (Cash and Equivalents And Restricted Cash) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Restricted Cash and Cash Equivalents	$ 5.5	$ 6.2	$ 6.2	$ 5.8	$ 6.0	$ 6.4
Restricted Cash and Cash Equivalents, Asset, Statement of Financial Position [Extensible List]	Other Assets, Noncurrent	Other Assets, Noncurrent	Other Assets, Noncurrent	Other Assets, Noncurrent	Other Assets, Noncurrent	Other Assets, Noncurrent