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Income Taxes (Summary Of Deferred Tax Assets And Deferred Tax Liabilities) (Details) - USD ($) $ in Thousands | Dec. 31, 2015 | Dec. 31, 2014
--- | --- | ---
Deferred tax assets |  |
Property costs and asset retirement obligations | $ 2,666 | $ 2,157
Employee benefits | 9,647 | 9,712
Other deferred tax assets | 7,297 | 8,995
Total gross deferred tax assets | 19,610 | 20,864
Less valuation allowance | 0 | 0
Net deferred tax assets | 19,610 | 20,864
Deferred tax liabilities |  |
Accumulated depreciation and amortization | (157,322) | (133,535)
State deferred taxes | (17,042) | (16,855)
Other deferred tax liabilities | (8,211) | (8,837)
Total gross deferred tax liabilities | (182,575) | (159,227)
Net deferred tax liabilities | $ (162,965) | $ (138,363)

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