Regulatory Capital and Other Regulatory Matters (Depository Institutions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total assets	$ 196,392	$ 191,826	$ 182,114
Statutory accounting practices, statutory amount available for dividend payments	112
Ally Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total assets	186,100	181,900
Payments of dividends	$ 1,400	$ 3,200