Summary of Significant Accounting Policies (Schedule of Cash and Cash Equivalents) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and cash equivalents	$ 383.5	$ 16.0	$ 8.5	$ 187.4
Restricted cash and cash equivalents	477.4	380.2	382.7	330.3
Total cash, cash equivalents, restricted cash and restricted cash equivalents	$ 860.9	$ 396.2	$ 391.2	$ 517.7