Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense expressed as a percentage of average depreciable property	3.60%	3.60%	3.60%
Operating revenues
Minimum annual tolerance band percentage for future rate recovery or refund of fuel costs	2.00%
Cash and Cash Equivalents [Abstract]
Maximum number of months of remaining maturity at time of purchase to consider investments in certain instruments as cash equivalents	3 months
Accounts and Financing Receivable, after Allowance for Credit Loss, Current and Noncurrent [Abstract]
Accounts Receivable, Allowance for Credit Loss, Current	$ 8	$ 8
Alternative Revenue Programs [Abstract]
Maximum number of months following end of annual period in which revenues are earned to be included in incentive programs	24 months
Percentage of Average Annual Operating Revenues	1.20%
Number of Years Annual Operating Revenues are Averaged	3 years
Public Utilities, Inventory [Line Items]
Inventories	$ 27	15
Accounts Receivable, Allowance for Credit Loss, Current	8	8
Materials and supplies
Public Utilities, Inventory [Line Items]
Inventories	8	7
Fuel
Public Utilities, Inventory [Line Items]
Inventories	9	4
Natural gas
Public Utilities, Inventory [Line Items]
Inventories	$ 10	$ 4