Accounting Changes and Recent Accounting Pronouncements (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease ROU assets	$ 512.7
Operating leases	545.1
Finance lease ROU assets	531.0		$ 545.5
Finance lease liabilities	$ 617.1
Decrease to accumulated deficit				$ (5,897.5)	$ (6,217.6)
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease ROU assets		$ 545.1
Operating leases		558.1
Finance lease ROU assets		26.2
Finance lease liabilities		26.2
Decrease to accumulated deficit		1.2
Net reduction in ROU assets		$ 14.2