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Amount of other addition (reduction) in allowance reserve for credit loss.

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Amount, after recoveries, of loans and leases that have been written-off.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount of expense related to loss from loan transactions.

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Finance Receivables and Loans, Net (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses				$ 1,276				$ 1,144	$ 1,276	$ 1,144
Allowance for loan and lease losses, charge-offs									(1,433)	(1,392)
Allowance for loan and lease losses, recoveries									488	382
Allowance for loan and lease losses, net charge-offs									(945)	(1,010)
Provision for loan losses	$ 266	$ 233	$ 158	261	$ 294	$ 314	$ 269	271	918	1,148	$ 917
Allowance for loan and lease losses, other									7	6
Allowance for loan losses	1,242				1,276				1,242	1,276	1,144
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Allowance for loan losses, individually evaluated for impairment	123				77				123	77
Allowance for loan losses, collectively evaluated for impairment	1,119				1,199				1,119	1,199
Finance receivables and loans, net	129,926				122,893				129,926	122,893
Finance receivables and loans, individually evaluated for impairment	1,075				733				1,075	733
Finance receivables and loans, collectively evaluated for impairment	128,851				122,160				128,851	122,160
Consumer portfolio segment \| Automobile loan
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses				1,066				932	1,066	932
Allowance for loan and lease losses, charge-offs									(1,383)	(1,344)
Allowance for loan and lease losses, recoveries									456	358
Allowance for loan and lease losses, net charge-offs									(927)	(986)
Provision for loan losses									911	1,127
Allowance for loan and lease losses, other									2	7
Allowance for loan losses	1,048				1,066				1,048	1,066	932
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Allowance for loan losses, individually evaluated for impairment	44				36				44	36
Allowance for loan losses, collectively evaluated for impairment	1,004				1,030				1,004	1,030
Finance receivables and loans, net	70,539				68,071				70,539	68,071
Finance receivables and loans, individually evaluated for impairment	495				430				495	430
Finance receivables and loans, collectively evaluated for impairment	70,044				67,641				70,044	67,641
Consumer portfolio segment \| Residential mortgage
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses				79				91	79	91
Allowance for loan and lease losses, charge-offs									(35)	(30)
Allowance for loan and lease losses, recoveries									25	24
Allowance for loan and lease losses, net charge-offs									(10)	(6)
Provision for loan losses									(15)	(7)
Allowance for loan and lease losses, other									1	(1)
Allowance for loan losses	53				79				53	79	91
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Allowance for loan losses, individually evaluated for impairment	23				27				23	27
Allowance for loan losses, collectively evaluated for impairment	30				52				30	52
Finance receivables and loans, net	16,701				13,750				16,701	13,750
Finance receivables and loans, individually evaluated for impairment	231				231				231	231
Finance receivables and loans, collectively evaluated for impairment	16,470				13,519				16,470	13,519
Commercial portfolio segment \| Commercial loan
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses				$ 131				$ 121	131	121
Allowance for loan and lease losses, charge-offs									(15)	(18)
Allowance for loan and lease losses, recoveries									7	0
Allowance for loan and lease losses, net charge-offs									(8)	(18)
Provision for loan losses									22	28
Allowance for loan and lease losses, other									4	0
Allowance for loan losses	141				131				141	131	$ 121
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Allowance for loan losses, individually evaluated for impairment	56				14				56	14
Allowance for loan losses, collectively evaluated for impairment	85				117				85	117
Finance receivables and loans, net	42,686				41,072				42,686	41,072
Finance receivables and loans, individually evaluated for impairment	349				72				349	72
Finance receivables and loans, collectively evaluated for impairment	$ 42,337				$ 41,000				$ 42,337	$ 41,000