Summary of Significant Accounting Policies (Schedule of Cash and Cash Equivalents) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and cash equivalents	$ 45.7	$ 16.0	$ 25.7	$ 187.4
Restricted cash and cash equivalents	538.5	380.2	408.1	330.3
Total cash, cash equivalents, restricted cash and restricted cash equivalents	$ 584.2	$ 396.2	$ 433.8	$ 517.7