Summary of Significant Accounting Policies (Schedule of Cash and Cash Equivalents) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and cash equivalents	$ 13.3	$ 16.0	$ 8.9	$ 187.4
Restricted cash and cash equivalents	429.0	380.2	391.9	330.3
Total cash, cash equivalents, restricted cash and restricted cash equivalents	$ 442.3	$ 396.2	$ 400.8	$ 517.7