Fair Value (Fair Value of Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	$ 2,246	$ 1,899
Loans held-for-sale, net	425	108
Finance receivables and loans, net	125,357	121,617
Nonmarketable equity securities	1,235	1,233
Deposit liabilities	101,379	93,256
Short-term borrowings	7,338	11,413
Long-term debt	45,542	44,226
Deposit liabilities with no defined contractual maturities, carrying value		47,400
Deposit liabilities with no defined contractual maturities, fair value		45,200
Reported value measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	2,246	1,899
Loans held-for-sale, net	412	95
Finance receivables and loans, net	125,357	121,617
Nonmarketable equity securities	1,179	1,233
Deposit liabilities	50,300	45,869
Short-term borrowings	7,338	11,413
Long-term debt	45,542	44,226
Estimate of fair value measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	2,139	1,865
Finance receivables and loans, net	127,106	123,302
Short-term borrowings	7,342	11,417
Long-term debt	47,378	46,624
Estimate of fair value measurement \| Fair value, inputs, level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	0	0
Finance receivables and loans, net	0	0
Short-term borrowings	0	0
Long-term debt	0	0
Estimate of fair value measurement \| Fair value, inputs, level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	2,139	1,865
Finance receivables and loans, net	0	0
Short-term borrowings	0	0
Long-term debt	26,425	27,807
Estimate of fair value measurement \| Fair value, inputs, level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	0	0
Finance receivables and loans, net	127,106	123,302
Short-term borrowings	7,342	11,417
Long-term debt	20,953	18,817
Portion at fair value measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-sale, net	419	95
Nonmarketable equity securities	1,179	1,239
Deposit liabilities	50,128	45,827
Portion at fair value measurement \| Fair value, inputs, level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-sale, net	0	0
Nonmarketable equity securities	0	0
Deposit liabilities	0	0
Portion at fair value measurement \| Fair value, inputs, level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-sale, net	0	0
Nonmarketable equity securities	1,179	1,190
Deposit liabilities	0	0
Portion at fair value measurement \| Fair value, inputs, level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-sale, net	419	95
Nonmarketable equity securities	0	49
Deposit liabilities	$ 50,128	$ 45,827

Carrying Value of Deposit Liabilities with no Defined Contractual Maturities

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Fair Value of Deposit Liabilities With No Defined Contractual Maturities

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Nonmarketable equity securities

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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Amount of investment in debt security measured at amortized cost (held-to-maturity).

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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