Other Assets (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Goodwill [Line Items]
Gain (loss) on nonmarketable equity investments, net	$ 2	$ (11)
Goodwill impairment			$ 149
Goodwill, transfers			4
Corporate and Other
Goodwill [Line Items]
Goodwill impairment			149
Goodwill, transfers			4
Corporate and Other | Disposal Group, Held-for-Sale or Disposed of by Sale, Not Discontinued Operations | Ally Lending
Goodwill [Line Items]
Goodwill impairment			$ 149