Fair Value (Fair Value of Financial Instruments) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	$ 1,189	$ 839
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	17	0
Loans and Leases Receivable, Net Amount	119,303	117,800
Nonmarketable equity securities	938	1,046
Deposits	86,183	79,022
Short-term Debt	10,712	12,673
Long-term Debt	49,145	54,128
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	1,189	839
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	17
Loans and Leases Receivable, Net Amount	119,303	117,800
Nonmarketable equity securities	925	1,046
Deposits	86,183	79,022
Short-term Debt	10,712	12,673
Long-term Debt	49,145	54,128
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	1,156	789
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	17
Loans and Leases Receivable, Net Amount	121,029	118,750
Nonmarketable equity securities	923	1,067
Deposits	84,287	78,469
Short-term Debt	10,714	12,675
Long-term Debt	51,534	56,120
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	0	0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0
Loans and Leases Receivable, Net Amount	0	0
Nonmarketable equity securities	0	0
Deposits	0	0
Short-term Debt	0	0
Long-term Debt	0	0
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	1,156	789
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0
Loans and Leases Receivable, Net Amount	0	0
Nonmarketable equity securities	898	1,012
Deposits	0	0
Short-term Debt	0	0
Long-term Debt	32,371	22,036
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	0	0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	17
Loans and Leases Receivable, Net Amount	121,029	118,750
Nonmarketable equity securities	25	55
Deposits	84,287	78,469
Short-term Debt	10,714	12,675
Long-term Debt	19,163	$ 34,084
Equity Securities [Member] \| Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nonmarketable equity securities	13
Equity Securities [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nonmarketable equity securities	$ 34

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 after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as 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.

+ References

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Amount, after allowance for bad debt, of loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

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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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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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