Regulatory Matters - Regulatory Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 7,214	$ 7,475
Regulatory liabilities	254	254
Regulatory liabilities, noncurrent	6,960	7,221
Deferred income taxes
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 3,185	3,600
Cost of removal
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	26 years
Total regulatory liabilities	$ 2,424	2,435
Asset retirement obligations
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	31 years
Total regulatory liabilities	$ 345	305
Levelized depreciation
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	29 years
Total regulatory liabilities	$ 259	281
Employee benefit plans
Regulatory Liabilities [Line Items]
Total regulatory liabilities	243	187
Other
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 758	$ 667