Other Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Goodwill [Line Items]
Proportional amortization investments	$ 2,143	$ 2,131		$ 2,143		$ 2,131
Unfunded commitments for proportional amortization investments	963	1,019		$ 963		1,019
Unfunded commitments, period to be paid				5 years
Goodwill impairment	$ 0		$ 0	$ 305	$ 0	118
Goodwill, transfers				56
Corporate and Other
Goodwill [Line Items]
Goodwill impairment				305		118
Goodwill, transfers				56
Corporate and Other | Disposal Group, Held-for-Sale or Disposed of by Sale, Not Discontinued Operations | Ally Credit Card
Goodwill [Line Items]
Goodwill impairment		$ 118		$ 305		$ 118