Summary of Significant Accounting Policies (Schedule of Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 19.7	$ 25.7	$ 55.7	$ 8.2
Restricted cash and cash equivalents	328.8	303.6	338.0	255.6
Total cash, cash equivalents, restricted cash and restricted cash equivalents	$ 348.5	$ 329.3	$ 393.7	$ 263.8