Summarized Quarterly Financial Data (Unaudited) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Regulated and Unregulated Operating Revenue	$ 248	$ 251	$ 218	$ 257	$ 248	$ 251	$ 218	$ 257	$ 1,105	$ 974	$ 981
Operating income	31	46	23	41	31	46	23	41	174	141	131
Net income	$ 21	$ 40	$ 12	$ 34	$ 21	$ 40	$ 12	$ 34	$ 108	$ 107	$ 79