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Income Taxes (Summary Of Deferred Tax Assets And Deferred Tax Liabilities) (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Deferred tax assets |  |
Property costs and asset retirement obligations | $ 4.5 | $ 3.7
Employee benefits | 8.0 | 6.1
Operating leases liability | 31.6 | 25.0
Other deferred tax assets | 7.2 | 2.1
Total gross deferred tax assets | 51.3 | 36.9
Deferred tax liabilities |  |
Accumulated depreciation and amortization | (213.2) | (191.2)
State deferred taxes | (20.2) | (27.9)
Operating leases right of use assets | (31.0) | (24.8)
Other deferred tax liabilities | (5.3) | (9.7)
Total gross deferred tax liabilities | (269.7) | (253.6)
Net deferred tax liabilities | $ (218.4) | $ (216.7)

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