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 |