Regulatory Matters - PAC - 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
Deferred income taxes
Regulatory Liabilities [Line Items]
Total regulatory liabilities	3,185	3,600
PAC
Regulatory Liabilities [Line Items]
Total regulatory liabilities	2,768	2,842
Regulatory liabilities	118	115
Regulatory liabilities, noncurrent	$ 2,650	2,727
PAC | Cost of removal
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	26 years
Total regulatory liabilities	$ 1,187	1,125
Regulatory liabilities, noncurrent	1,187	1,125
PAC | Deferred income taxes
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 1,307	1,463
PAC | Unrealized gain on regulated derivatives
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	1 year
Total regulatory liabilities	$ 53	0
PAC | Other
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 221	$ 254