Finance Receivables and Loans, Net (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	$ 1,089	$ 974	$ 1,054	$ 977
Allowance for Loan and Lease Losses, Write-offs	(303)	(231)	(803)	(621)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	90	70	259	210
Allowance for Loan and Lease Losses Write-offs, Net	(213)	(161)	(544)	(411)
Allowance for Loan and Lease Losses, Provision for Loss, Net	(258)	(211)	(650)	(467)
Allowance for Loan and Lease Losses, Adjustments, Net		6	26	15
Loans and Leases Receivable, Allowance, Ending Balance	1,134	1,018	1,134	1,018
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	84	89	84	89
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,050	929	1,050	929
Loans and Leases Receivable, Gross	114,959	107,990	114,959	107,990	$ 111,600
Financing Receivable, Individually Evaluated for Impairment	711	628	711	628
Financing Receivable, Collectively Evaluated for Impairment	114,248	107,362	114,248	107,362
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses	0	0	0	0
Loans and Leases Receivable, Gross	0	0	0	0
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	862	767	834	685
Allowance for Loan and Lease Losses, Write-offs	(293)	(220)	(773)	(579)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	74	64	233	195
Allowance for Loan and Lease Losses Write-offs, Net	(219)	(156)	(540)	(384)
Allowance for Loan and Lease Losses, Provision for Loss, Net	(269)	(200)	(644)	(510)
Allowance for Loan and Lease Losses, Adjustments, Net		7	26	7
Loans and Leases Receivable, Allowance, Ending Balance	912	804	912	804
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	24	22	24	22
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	888	782	888	782
Loans and Leases Receivable, Gross	64,816	63,610	64,816	63,610	64,292
Financing Receivable, Individually Evaluated for Impairment	349	285	349	285
Financing Receivable, Collectively Evaluated for Impairment	64,467	63,325	64,467	63,325
Consumer Portfolio Segment [Member] | Automobile Loan [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses	0	0	0	0
Loans and Leases Receivable, Gross	0	0	0	0
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	109	119	114	152
Allowance for Loan and Lease Losses, Write-offs	(10)	(10)	(29)	(41)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	16	4	25	12
Allowance for Loan and Lease Losses Write-offs, Net	6	(6)	(4)	(29)
Allowance for Loan and Lease Losses, Provision for Loss, Net	15	(6)	10	(4)
Allowance for Loan and Lease Losses, Adjustments, Net		0	0	8
Loans and Leases Receivable, Allowance, Ending Balance	100	119	100	119
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	35	48	35	48
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	65	71	65	71
Loans and Leases Receivable, Gross	10,857	9,769	10,857	9,769	9,773
Financing Receivable, Individually Evaluated for Impairment	251	268	251	268
Financing Receivable, Collectively Evaluated for Impairment	10,606	9,501	10,606	9,501
Consumer Portfolio Segment [Member] | Residential Mortgage [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses	0	0	0	0
Loans and Leases Receivable, Gross	0	0	0	0
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	118	88	106	140
Allowance for Loan and Lease Losses, Write-offs	0	(1)	(1)	(1)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	0	2	1	3
Allowance for Loan and Lease Losses Write-offs, Net	0	1	0	2
Allowance for Loan and Lease Losses, Provision for Loss, Net	(4)	(5)	(16)	47
Allowance for Loan and Lease Losses, Adjustments, Net		(1)	0	0
Loans and Leases Receivable, Allowance, Ending Balance	122	95	122	95
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	25	19	25	19
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	97	76	97	76
Loans and Leases Receivable, Gross	39,286	34,611	39,286	34,611	$ 37,535
Financing Receivable, Individually Evaluated for Impairment	111	75	111	75
Financing Receivable, Collectively Evaluated for Impairment	39,175	34,536	39,175	34,536
Commercial Portfolio Segment [Member] | Commercial Loan [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses	0	0	0	0
Loans and Leases Receivable, Gross	$ 0	$ 0	$ 0	$ 0