Income Taxes Schedule of Deferred tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred income tax assets:
Employee benefits	$ 136	$ 119
Price risk management	29	26
Deferred income taxes	23	22
Deferred Tax Assets, tax credits, net of valuation allowance	77	64
Total deferred income tax assets	265	231
Deferred income tax liabilities:
Depreciation and amortization	504	496
Regulatory assets	128	103
Deferred Tax Liabilities, Other	7	10
Deferred Tax Liabilities, Gross, Noncurrent	639	609
Total deferred income tax liabilities	$ 374	$ 378