Summary of Significant Accounting Policies (Schedule of Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Cash and cash equivalents	$ 3.1	$ 7.7	$ 10.7	$ 23.3
Restricted cash and cash equivalents	435.1	410.0	384.7	410.9
Total cash, cash equivalents, restricted cash and restricted cash equivalents	$ 438.2	$ 417.7	$ 395.4	$ 434.2