Finance Receivables and Loans, Net (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance	$ 3,152	$ 3,245	$ 3,283	$ 1,263
Charge-offs	(197)	(291)	(505)	(675)
Recoveries	203	113	393	231
Net charge-offs	6	(178)	(112)	(444)
Provision for credit losses	(32)	287	(45)	1,190
Other	0	0	0	(1)
Allowance, ending balance	3,126	3,354	3,126	3,354
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance				1,346
Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance				2,609
Consumer | Consumer automotive
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance	2,809	2,833	2,902	1,075
Charge-offs	(183)	(245)	(467)	(618)
Recoveries	188	108	375	219
Net charge-offs	5	(137)	(92)	(399)
Provision for credit losses	(12)	269	(8)	954
Other	0	(2)	0	(1)
Allowance, ending balance	2,802	2,963	2,802	2,963
Consumer | Consumer automotive | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance				1,334
Consumer | Consumer automotive | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance				2,409
Consumer | Consumer mortgage
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance	26	39	33	46
Charge-offs	(2)	(2)	(4)	(5)
Recoveries	3	4	6	9
Net charge-offs	1	2	2	4
Provision for credit losses	(4)	1	(11)	(2)
Other	1	0	0	0
Allowance, ending balance	24	42	24	42
Consumer | Consumer mortgage | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance				(6)
Consumer | Consumer mortgage | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance				40
Consumer | Consumer other
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance	69	45	73	9
Charge-offs	(5)	(4)	(13)	(9)
Recoveries	1	0	1	1
Net charge-offs	(4)	(4)	(12)	(8)
Provision for credit losses	8	6	11	31
Other	(1)	2	0	1
Allowance, ending balance	72	49	72	49
Consumer | Consumer other | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance				16
Consumer | Consumer other | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance				25
Commercial
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance	248	328	275	133
Charge-offs	(7)	(40)	(21)	(43)
Recoveries	11	1	11	2
Net charge-offs	4	(39)	(10)	(41)
Provision for credit losses	(24)	11	(37)	207
Other	0	0	0	(1)
Allowance, ending balance	$ 228	$ 300	$ 228	300
Commercial | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance				2
Commercial | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance				$ 135