Long-Term Debt (Senior Unsecured Debt) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Principal Outstanding	$ 16,762	$ 17,516
Less: Debt subject to compromise	(10,949)
Total debt	5,813	17,516
Secured Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	4,957	5,711
Secured Debt [Member] \| Revolver Due 2/27/2024 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 749	$ 749
Interest Rate		4.76%
Debt instrument, maturity date	Feb. 27, 2024
Secured Debt [Member] \| Term Loan Due 6/15/2024 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 1,694	$ 1,699
Interest Rate	6.00%	5.55%
Debt instrument, maturity date	Jun. 15, 2024
Secured Debt [Member] \| First Lien Notes Due 4/1/2027 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 1,650	$ 1,650
Interest Rate	8.00%	8.00%
Debt instrument, maturity date	Apr. 01, 2027
Secured Debt [Member] \| Second Lien Notes Due 4/1/2026 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 1,600	$ 1,600
Interest Rate	8.50%	8.50%
Debt instrument, maturity date	Apr. 01, 2026
Secured Debt [Member] \| IDRB Due 5/1/2030 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 13	$ 13
Interest Rate	6.20%	6.20%
Debt instrument, maturity date	May 01, 2030
Unsecured Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 10,949	$ 10,949
Unsecured Debt [Member] \| Senior Note Due 4/15/2020 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 172	$ 172
Interest Rate	8.50%	8.50%
Debt instrument, maturity date	Apr. 15, 2020
Unsecured Debt [Member] \| Senior Note Due 9/15/2020 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 55	$ 55
Interest Rate	8.875%	8.875%
Debt instrument, maturity date	Sep. 15, 2020
Unsecured Debt [Member] \| Senior Note Due 7/1/2021 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 89	$ 89
Interest Rate	9.25%	9.25%
Debt instrument, maturity date	Jul. 01, 2021
Unsecured Debt [Member] \| Senior Note Due 9/15/2021 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 220	$ 220
Interest Rate	6.25%	6.25%
Debt instrument, maturity date	Sep. 15, 2021
Unsecured Debt [Member] \| Senior Note Due 4/15/2022 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 500	$ 500
Interest Rate	8.75%	8.75%
Debt instrument, maturity date	Apr. 15, 2022
Unsecured Debt [Member] \| Senior Note Due 9/15/2022 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 2,188	$ 2,188
Interest Rate	10.50%	10.50%
Debt instrument, maturity date	Sep. 15, 2022
Unsecured Debt [Member] \| Senior Note Due 1/15/2023 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 850	$ 850
Interest Rate	7.125%	7.125%
Debt instrument, maturity date	Jan. 15, 2023
Unsecured Debt [Member] \| Senior Note Due 4/15/2024 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 750	$ 750
Interest Rate	7.625%
Debt instrument, maturity date	Apr. 15, 2024
Unsecured Debt [Member] \| Senior Note Due 1/15/2025 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 775	$ 775
Interest Rate	6.875%	6.875%
Debt instrument, maturity date	Jan. 15, 2025
Unsecured Debt [Member] \| Senior Note Due 9/15/2025 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 3,600	$ 3,600
Interest Rate	11.00%	11.00%
Debt instrument, maturity date	Sep. 15, 2025
Unsecured Debt [Member] \| Debenture Due 11/1/2025 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 138	$ 138
Interest Rate	7.00%	7.00%
Debt instrument, maturity date	Nov. 01, 2025
Unsecured Debt [Member] \| Debenture Due 8/15/2026 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 2	$ 2
Interest Rate	6.80%	6.80%
Debt instrument, maturity date	Aug. 15, 2026
Unsecured Debt [Member] \| Senior Note Due 1/15/2027 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 346	$ 346
Interest Rate	7.875%	7.875%
Debt instrument, maturity date	Jan. 15, 2027
Unsecured Debt [Member] \| Senior Note Due 8/15/2031 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 945	$ 945
Interest Rate	9.00%	9.00%
Debt instrument, maturity date	Aug. 15, 2031
Unsecured Debt [Member] \| Debenture Due 10/1/2034 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 1	$ 1
Interest Rate	7.68%	7.68%
Debt instrument, maturity date	Oct. 01, 2034
Unsecured Debt [Member] \| Debenture Due 7/1/2035 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 125	$ 125
Interest Rate	7.45%	7.45%
Debt instrument, maturity date	Jul. 01, 2035
Unsecured Debt [Member] \| Debenture Due 10/1/2046 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 193	$ 193
Interest Rate	7.05%	7.05%
Debt instrument, maturity date	Oct. 01, 2046
Secured Subsidiary Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 106	$ 106
Secured Subsidiary Debt [Member] \| Debenture Due 11/15/2031 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 100	$ 100
Interest Rate	8.50%	8.50%
Debt instrument, maturity date	Nov. 15, 2031
Secured Subsidiary Debt [Member] \| RUS Loan Contracts Due 1/3/2028 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 6	$ 6
Interest Rate	6.154%	6.154%
Debt instrument, maturity date	Jan. 03, 2028
Unsecured Subsidiary Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 750	$ 750
Unsecured Subsidiary Debt [Member] \| Debenture Due 5/15/2027 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 200	$ 200
Interest Rate	6.75%	6.75%
Debt instrument, maturity date	May 15, 2027
Unsecured Subsidiary Debt [Member] \| Debenture Due 2/1/2028 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 300	$ 300
Interest Rate	6.86%	6.86%
Debt instrument, maturity date	Feb. 01, 2028
Unsecured Subsidiary Debt [Member] \| Debenture Due 2/15/2028 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 200	$ 200
Interest Rate	6.73%	6.73%
Debt instrument, maturity date	Feb. 15, 2028
Unsecured Subsidiary Debt [Member] \| Debenture Due 10/15/2029 [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 50	$ 50
Interest Rate	8.40%	8.40%
Debt instrument, maturity date	Oct. 15, 2029
Secured Debt, Unsecured Debt, Secured Subsidiary Debt, And Unsecured Subsidiary Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 16,762	$ 17,516
Weighted average interest rate	8.699%	8.486%

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

Name:	us-gaap_LongtermDebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant