Held-for-sale Operations - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Provision for credit losses	$ 1,979	$ 1,396
Goodwill impairment	149	$ 0	$ 0
Corporate and Other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill impairment	149
Disposal Group, Held-for-Sale, Not Discontinued Operations | Ally Lending
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Provision for credit losses	16
Net pretax loss	133
Disposal Group, Held-for-Sale, Not Discontinued Operations | Ally Lending | Corporate and Other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill impairment	$ 149