Summary of Significant Accounting Policies (Cash) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Money market funds	$ 329	$ 62
Cash and cash equivalents	390	87
Short-term restricted cash	4	2
Total cash, cash equivalents, and restricted cash	394	89	$ 70	$ 152
SCE
Restricted Cash and Cash Equivalents Items [Line Items]
Money market funds	230	38
Cash and cash equivalents	279	55
Short-term restricted cash	1	1
Total cash, cash equivalents, and restricted cash	$ 280	$ 56	$ 24	$ 22