Goodwill and Other Intangible Assets - Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 349	$ 785
Deconsolidation of Altium Packaging (see Note 2)		(436)
Other adjustments	(3)
Goodwill, ending balance	346	349
Corporate
Goodwill [Roll Forward]
Goodwill, beginning balance	0	436
Deconsolidation of Altium Packaging (see Note 2)		(436)
Other adjustments
Goodwill, ending balance	0	0
CNA Financial | Operating Segments
Goodwill [Roll Forward]
Goodwill, beginning balance	112	112
Other adjustments	(3)
Goodwill, ending balance	109	112
Boardwalk Pipelines | Operating Segments
Goodwill [Roll Forward]
Goodwill, beginning balance	237	237
Other adjustments
Goodwill, ending balance	$ 237	$ 237