Summary of Significant Accounting Policies (Cash) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Restricted Cash and Cash Equivalents Items [Line Items]
Money market funds	$ 167	$ 329
Cash and cash equivalents	231	390
Short-term restricted cash	3	4
Total cash, cash equivalents, and restricted cash	234	394	$ 390	$ 89
SCE
Restricted Cash and Cash Equivalents Items [Line Items]
Money market funds	63	230
Cash and cash equivalents	119	279
Short-term restricted cash		1
Total cash, cash equivalents, and restricted cash	$ 119	$ 280	$ 26	$ 56