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Income Taxes Schedule of Deferred tax Assets and Liabilities (Details) - USD ($) $ in Millions | Dec. 31, 2016 | Dec. 31, 2015
--- | --- | ---
Deferred income tax assets: |  |
Employee benefits | $ 181 | $ 170
Price risk management | 59 | 112
Deferred income taxes | 29 | 42
Deferred Tax Assets, tax credits, net of valuation allowance | 56 | 46
Deferred Tax Assets, Tax Deferred Expense, Other | 5 | 0
Total deferred income tax assets | 330 | 370
Deferred income tax liabilities: |  |
Depreciation and amortization | 829 | 781
Regulatory assets | 170 | 220
Deferred Tax Liabilities, Other | 0 | 1
Deferred Tax Liabilities, Gross, Noncurrent | 999 | 1,002
Total deferred income tax liabilities | $ (669) | $ (632)

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