Long-Term Debt (Long-Term Debt) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt, beginning balance	$ 16,769
Payments and Retirements
New Borrowings
Long-term debt, ending balance	16,769
Less: Debt Issuance Costs
Less: Debt Discount	(38)	(39)
Debt, less unamortized debt issuance costs and discounts	16,731	16,730
Less: Current Portion	(5,782)	(5,781)
Less: Debt subject to compromise	(10,949)	(10,949)
Total Long-Term Debt
Interest Rate	8.07%
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance	$ 4,964
Long-term debt, ending balance	4,964
Secured Debt [Member] \| Parent Company [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance	4,964
Payments and Retirements
New Borrowings
Long-term debt, ending balance	$ 4,964
Interest Rate	5.75%
Secured Debt [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance	$ 106
Payments and Retirements
New Borrowings
Long-term debt, ending balance	$ 106
Interest Rate	8.37%
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance	$ 10,949
Long-term debt, ending balance	10,949
Unsecured Debt [Member] \| Parent Company [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance	10,949
Payments and Retirements
New Borrowings
Long-term debt, ending balance	$ 10,949
Interest Rate	9.19%
Unsecured Debt [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance	$ 750
Payments and Retirements
New Borrowings
Long-term debt, ending balance	$ 750
Interest Rate	6.90%

Debt Instrument, Less Amortized Debt Issuance Costs And Discounts

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- Definition

Liabilities Subject To Compromise Debt

+ References

No definition available.

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- Definition

Weighted average interest rate of long-term debt including debt issuance costs, premiums and or discounts.

+ References

No definition available.

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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.

+ References

No definition available.

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- Definition

Amount, after accumulated amortization, of debt discount (premium).

+ References

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-Name Accounting Standards Codification
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- Definition

Amount, after accumulated amortization, of debt issuance costs classified as current. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

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- Definition

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.

+ References

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- Definition

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.

+ References

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- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

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