Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total long-term debt	$ 34,027	$ 44,193
Debt Instrument, Interest Rate, Stated Percentage	8.125%
Subordinated Debt	$ 1,000	1,000
Secured Debt	25,773	39,596
Long-term debt, due within one year	9,219	8,976
Long-term debt, due after one year	24,808	35,217
Debt converted from fixed-rate into variable-rate	7,000	0
Unsecured debt
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Amount	8,566	9,406
Long-term Debt, Percentage Bearing Variable Interest, Amount	1	1
Trust preferred securities	2,575	2,572
Long-term Debt, Fair Value Hedge Basis Adjustment	62	128
Total long-term debt	$ 11,204	$ 12,107
Debt, Weighted Average Interest Rate	6.34%	6.29%
Long-term debt, due within one year	$ 2,214	$ 1,663
Long-term debt, due after one year	$ 8,990	$ 10,444
Unsecured debt \| Minimum
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.71%	2.42%
Unsecured debt \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.00%	8.40%
Secured debt
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Amount	$ 21,477	$ 23,514
Long-term Debt, Percentage Bearing Variable Interest, Amount	1,384	8,633
Long-term Debt, Fair Value Hedge Basis Adjustment	(38)	(61)
Total long-term debt	$ 22,823	$ 32,086
Debt, Weighted Average Interest Rate	2.44%	2.54%
Long-term Debt, No stated interest rate	$ 92	$ 5
Variable Interest Entity Debt	9,100	10,500
Long-term debt, due within one year	7,005	7,313
Long-term debt, due after one year	15,818	24,773
Secured debt \| Committed funding facilities
Debt Instrument [Line Items]
Long-term line of credit	$ 450	$ 6,665
Secured debt \| Minimum
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.35%	1.26%
Secured debt \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.03%	4.50%
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Secured Debt	$ 13,300	$ 14,900

Debt converted from fixed-rate into variable-rate

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- Definition

Long-term Debt, Fair Value Hedge Basis Adjustment

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Long-term Debt, No stated interest rate

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- Definition

Trust preferred securities

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- Definition

Variable Interest Entity Debt

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Weighted average interest rate of debt outstanding.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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