Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash, Cash Equivalents and Restricted Cash:
Cash and cash equivalents	$ 2,025.7	$ 334.7
Restricted cash	89.9	75.3
Total cash, cash equivalents and restricted cash shown in the Unaudited Condensed Statements of Consolidated Cash Flows	$ 2,115.6	$ 410.0	$ 107.5	$ 410.1