Summary of Significant Accounting Policies (Impact of Adoption of Topic 842) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets	$ 147.0	$ 144.8
Operating lease liabilities	171.9	$ 174.5
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets	$ 147.0