Finance Receivables and Loans, Net (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	$ 1,144	$ 1,054
Allowance for Loan and Lease Losses, Write-offs	(350)	(263)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	97	84
Allowance for Loan and Lease Losses Write-offs, Net	(253)	(179)
Provision for Loan and Lease Losses	(271)	(220)
Allowance for Loan and Lease Losses, Adjustments, Other	7	18
Loans and Leases Receivable, Allowance, Ending Balance	1,155	1,077
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	89	86
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,066	991
Loans and Leases Receivable, Gross	119,002	110,876	$ 118,944
Financing Receivable, Individually Evaluated for Impairment	757	688
Financing Receivable, Collectively Evaluated for Impairment	118,245	110,188
Consumer Portfolio Segment [Member] \| Automobile Loan [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	932	834
Allowance for Loan and Lease Losses, Write-offs	(341)	(253)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	90	80
Allowance for Loan and Lease Losses Write-offs, Net	(251)	(173)
Provision for Loan and Lease Losses	(267)	(207)
Allowance for Loan and Lease Losses, Adjustments, Other	7	18
Loans and Leases Receivable, Allowance, Ending Balance	941	850
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	32	25
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	909	825
Loans and Leases Receivable, Gross	65,663	63,013	65,793
Financing Receivable, Individually Evaluated for Impairment	388	337
Financing Receivable, Collectively Evaluated for Impairment	65,275	62,676
Consumer Portfolio Segment [Member] \| Residential Mortgage [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	91	114
Allowance for Loan and Lease Losses, Write-offs	(9)	(10)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	7	4
Allowance for Loan and Lease Losses Write-offs, Net	(2)	(6)
Provision for Loan and Lease Losses	3	(7)
Allowance for Loan and Lease Losses, Adjustments, Other	0	0
Loans and Leases Receivable, Allowance, Ending Balance	86	115
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	33	43
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	53	72
Loans and Leases Receivable, Gross	10,937	10,675	11,050
Financing Receivable, Individually Evaluated for Impairment	249	261
Financing Receivable, Collectively Evaluated for Impairment	10,688	10,414
Commercial Portfolio Segment [Member] \| Commercial Loan [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	121	106
Allowance for Loan and Lease Losses, Write-offs	0	0
Allowance for Loan and Lease Loss, Recovery of Bad Debts	0	0
Allowance for Loan and Lease Losses Write-offs, Net	0	0
Provision for Loan and Lease Losses	(7)	(6)
Allowance for Loan and Lease Losses, Adjustments, Other	0	0
Loans and Leases Receivable, Allowance, Ending Balance	128	112
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	24	18
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	104	94
Loans and Leases Receivable, Gross	42,402	37,188	$ 42,101
Financing Receivable, Individually Evaluated for Impairment	120	90
Financing Receivable, Collectively Evaluated for Impairment	$ 42,282	$ 37,098

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and 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 valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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

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

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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 estimated loss from loan and lease transactions.

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