Summary of Significant Accounting Policies (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($) segment	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Operating lease assets	$ 434.4		$ 0.0
Operating lease liabilities	$ 495.3
Number of reportable segments | segment	1
Interest in subsidiary (less than given percentage)	100.00%
Accounting Standards Update 2016-02
Operating lease assets		$ 463.0
Operating lease liabilities		$ 526.0