Finance Receivables and Loans, Net (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance, beginning balance	$ 3,267	$ 3,283
Charge-offs	(1,628)	(981)
Recoveries	676	712
Net charge-offs	(952)	(269)
Provision for credit losses	1,396	241
Other	0	12
Allowance, ending balance	3,711	3,267
Unfunded Loan Commitment
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Provision for credit losses	3
Consumer | Automotive
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance, beginning balance	2,769	2,902
Charge-offs	(1,434)	(923)
Recoveries	649	686
Net charge-offs	(785)	(237)
Provision for credit losses	1,036	104
Other	0	0
Allowance, ending balance	3,020	2,769
Consumer | Consumer mortgage
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance, beginning balance	27	33
Charge-offs	(3)	(6)
Recoveries	12	13
Net charge-offs	9	7
Provision for credit losses	(8)	(14)
Other	(1)	1
Allowance, ending balance	27	27
Consumer | Consumer other
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance, beginning balance	221	73
Charge-offs	(133)	(30)
Recoveries	12	2
Net charge-offs	(121)	(28)
Provision for credit losses	326	163
Other	0	13
Allowance, ending balance	426	221
Fair value, option, carrying amount, financing receivable, no allowance	3	7	$ 8
Consumer | Consumer other | Ally Credit Card
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Financing receivable, purchased with credit deterioration, allowance for credit loss		97
Financing receivable, excluding accrued interest, purchased with credit deterioration, allowance for credit loss at acquisition date		12
Commercial
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance, beginning balance	250	275
Charge-offs	(58)	(22)
Recoveries	3	11
Net charge-offs	(55)	(11)
Provision for credit losses	42	(12)
Other	1	(2)
Allowance, ending balance	$ 238	$ 250