Finance Receivables and Loans, Net (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, Beginning Balance	$ 1,054	$ 977
Allowance for Loan and Lease Losses, Write-offs	(1,142)	(892)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	341	283
Allowance for Loan and Lease Losses Write-offs, Net	(801)	(609)
Allowance for Loan and Lease Losses, Provision for Loss, Net	(917)	(707)
Allowance for Loan and Lease Losses, Adjustments, Net	26	21
Loans and Leases Receivable, Allowance, Ending Balance	1,144	1,054
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	85	86
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,059	968
Loans and Leases Receivable, Gross	118,944	111,600
Financing Receivable, Individually Evaluated for Impairment	739	658
Financing Receivable, Collectively Evaluated for Impairment	118,205	110,942
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses	0	0
Loans and Leases Receivable, Gross	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	834	685
Allowance for Loan and Lease Losses, Write-offs	(1,102)	(840)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	307	262
Allowance for Loan and Lease Losses Write-offs, Net	(795)	(578)
Allowance for Loan and Lease Losses, Provision for Loss, Net	(919)	(739)
Allowance for Loan and Lease Losses, Adjustments, Net	26	12
Loans and Leases Receivable, Allowance, Ending Balance	932	834
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	28	22
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	904	812
Loans and Leases Receivable, Gross	65,793	64,292
Financing Receivable, Individually Evaluated for Impairment	370	315
Financing Receivable, Collectively Evaluated for Impairment	65,423	63,977
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
Loans and Leases Receivable, Gross	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	114	152
Allowance for Loan and Lease Losses, Write-offs	(39)	(48)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	32	17
Allowance for Loan and Lease Losses Write-offs, Net	(7)	(31)
Allowance for Loan and Lease Losses, Provision for Loss, Net	16	(1)
Allowance for Loan and Lease Losses, Adjustments, Net	0	8
Loans and Leases Receivable, Allowance, Ending Balance	91	114
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	34	44
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	57	70
Loans and Leases Receivable, Gross	11,050	9,773
Financing Receivable, Individually Evaluated for Impairment	247	266
Financing Receivable, Collectively Evaluated for Impairment	10,803	9,507
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
Loans and Leases Receivable, Gross	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	106	140
Allowance for Loan and Lease Losses, Write-offs	(1)	(4)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	2	4
Allowance for Loan and Lease Losses Write-offs, Net	1	0
Allowance for Loan and Lease Losses, Provision for Loss, Net	(14)	33
Allowance for Loan and Lease Losses, Adjustments, Net	0	1
Loans and Leases Receivable, Allowance, Ending Balance	121	106
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	23	20
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	98	86
Loans and Leases Receivable, Gross	42,101	37,535
Financing Receivable, Individually Evaluated for Impairment	122	77
Financing Receivable, Collectively Evaluated for Impairment	41,979	37,458
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
Loans and Leases Receivable, Gross	$ 0	$ 0

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

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
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-Publisher FASB
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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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A valuation allowance for financing receivables that are expected to be uncollectible.

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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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- Definition

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
-Name Accounting Standards Codification
-Topic 310
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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

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-Publisher FASB
-Name Accounting Standards Codification
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