Recent Accounting Pronouncements Recent Accounting Pronouncements (Recently Adopted Accounting Pronouncements) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets	$ 144.8		$ 0.0
Operating lease liabilities	$ 174.5
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets		$ 118.8
Operating lease liabilities		145.8
Deferred rent		$ 27.9