Other Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2024
Goodwill [Line Items]
Proportional amortization investments	$ 2,168	$ 2,131		$ 2,131
Unfunded commitments for proportional amortization investments	$ 1,022	1,019		1,019
Unfunded commitments, period to be paid	5 years
Goodwill impairment	$ 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	$ 305	$ 118		$ 118