Long-Term Debt - Schedule of Debt (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt and lease obligations	$ 11,953	$ 12,216
Less: Unamortized deferred debt issuance costs and note premium	(459)	(250)
Less: Current maturities	(27)	(123)
Total long-term debt	11,926	12,093
Senior Secured Notes \| Senior Secured Notes at 6.25%, Due 2023
Debt Instrument [Line Items]
Debt and lease obligations		95
Senior Secured Notes \| Senior Secured Notes at 8.625%, Due 2024
Debt Instrument [Line Items]
Debt and lease obligations		1,033
Senior Secured Notes \| Senior Secured Notes at 6.625% Due 2025
Debt Instrument [Line Items]
Debt and lease obligations	1,462	1,462
Senior Secured Notes \| Senior Secured Notes at 8%, Due 2026
Debt Instrument [Line Items]
Debt and lease obligations	2,101	2,101
Senior Secured Notes \| Senior Secured Notes at 8% Due 2027
Debt Instrument [Line Items]
Debt and lease obligations	700	700
Senior Secured Notes \| Senior Secured Notes at 5.625% due 2027
Debt Instrument [Line Items]
Debt and lease obligations	1,900	1,900
Senior Secured Notes \| Senior Secured Notes at 6% due 2029
Debt Instrument [Line Items]
Debt and lease obligations	900	900
Senior Secured Notes \| Senior Secured Notes at 4.750% due 2031
Debt Instrument [Line Items]
Debt and lease obligations	1,095
Senior Notes \| Senior Notes at 6.875%, Due 2022
Debt Instrument [Line Items]
Debt and lease obligations		126
Senior Notes \| Senior Notes at 6.875% Due 2028
Debt Instrument [Line Items]
Debt and lease obligations	767	767
Junior-Priority Secured Notes \| Junior-Priority Secured Notes at 8.125% Due 2024
Debt Instrument [Line Items]
Debt and lease obligations		1,348
Junior-Priority Secured Notes \| Junior-Priority Secured Notes at 6.875% Due 2029
Debt Instrument [Line Items]
Debt and lease obligations	1,775
Junior-Priority Secured Notes \| Junior-Priority Secured Notes at 9.875% Due 2023
Debt Instrument [Line Items]
Debt and lease obligations		1,769
Junior-Priority Secured Notes \| Junior-Priority Secured Notes at 6.125% Due 2030
Debt Instrument [Line Items]
Debt and lease obligations	1,440
Finance Lease and Financing Obligations
Debt Instrument [Line Items]
Debt and lease obligations	249	239
Other
Debt Instrument [Line Items]
Debt and lease obligations	$ 23	$ 26

Amount of short-term and long-term debt and lease obligation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13,16)
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of unamortized debt discount (premium) and debt issuance costs.

+ 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)(2)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

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Amount of long-term debt and lease obligation, classified as current.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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