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	$ 1,134	$ 1,081	$ 911	$ 1,057	$ 1,134	$ 1,081	$ 911	$ 1,057	$ 4,815	$ 4,183	$ 4,237
Operating income	176	290	161	196	176	290	161	196	895	823	857
Net income	$ 133	$ 218	$ 108	$ 129	$ 133	$ 218	$ 108	$ 129	$ 660	$ 588	$ 578