Goodwill and Other Intangible Assets - Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2024
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 346
Other adjustments	1
Goodwill, ending balance	347
Goodwill	347	$ 347
CNA Financial
Goodwill [Roll Forward]
Goodwill, beginning balance	109
Other adjustments	1
Goodwill, ending balance	110
Goodwill	110	110
Boardwalk Pipelines
Goodwill [Roll Forward]
Goodwill, beginning balance	237
Other adjustments
Goodwill, ending balance	237
Goodwill	$ 237	$ 237