Other Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Goodwill [Line Items]
Proportional amortization investments	$ 2,034		$ 2,034		$ 1,866
Unfunded commitments for proportional amortization investments	980		$ 980		973
Unfunded commitments, period to be paid			5 years
Loss on nonmarketable equity investments, net	$ 0	$ 0	$ 9	$ 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