Description of the Business and Summary of Significant Accounting Policies (Cash and Equivalents, and Restricted Cash and Equivalents) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Description of the Business and Summary of Significant Accounting Policies
Restricted Cash and Cash Equivalents	$ 5.5	$ 5.9	$ 6.2	$ 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