Regulatory Matters - SPPC - 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
Cost of removal
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	26 years
Total regulatory liabilities	$ 2,424	2,435
Other
Regulatory Liabilities [Line Items]
Total regulatory liabilities	758	667
SPPC
Regulatory Liabilities [Line Items]
Total regulatory liabilities	463	497
Regulatory liabilities	19	34
Regulatory liabilities, noncurrent	444	463
SPPC | Deferred income taxes
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 234	249
SPPC | Cost of removal
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	36 years
Total regulatory liabilities	$ 201	197
SPPC | Other
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 28	$ 51