Goodwill and Other Intangible Assets - Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 346	$ 349
Other adjustments	1	(3)
Goodwill, ending balance	347	346
CNA Financial
Goodwill [Roll Forward]
Goodwill, beginning balance	109	112
Other adjustments	1	(3)
Goodwill, ending balance	110	109
Boardwalk Pipelines
Goodwill [Roll Forward]
Goodwill, beginning balance	237	237
Other adjustments
Goodwill, ending balance	$ 237	$ 237