Chapter 11 Filing And Other Related Matters (Narrative) (Details) - USD ($)					9 Months Ended
	Oct. 08, 2020	Aug. 27, 2020	Aug. 13, 2020	May 15, 2020	Sep. 30, 2020	Dec. 31, 2019
Reorganization [Line Items]
Takeback Debt, Principal amount		$ 750,000,000
Principal Outstanding					$ 16,762,000,000	$ 17,516,000,000
JP Morgan Revolving Credit Facility 2015 [Member]
Reorganization [Line Items]
Maturity date					Feb. 27, 2024
Debt instrument, face amount					$ 850,000,000
JP Morgan Term Loan B [Member]
Reorganization [Line Items]
Maturity date					Jun. 15, 2024
Debt instrument, face amount					$ 1,740,000,000
Secured Debt [Member]
Reorganization [Line Items]
Principal Outstanding					4,957,000,000	5,711,000,000
Unsecured Debt [Member]
Reorganization [Line Items]
Principal Outstanding					10,949,000,000	10,949,000,000
Secured Subsidiary Debt [Member]
Reorganization [Line Items]
Principal Outstanding					106,000,000	106,000,000
Unsecured Subsidiary Debt [Member]
Reorganization [Line Items]
Principal Outstanding					750,000,000	$ 750,000,000
Term Loan B [Member]
Reorganization [Line Items]
Payments to holders					48,200,000
Original First Lien Notes [Member]
Reorganization [Line Items]
Payments to holders					9,300,000
Term Loan B, Second Payment [Member]
Reorganization [Line Items]
Payments to holders					$ 7,500,000
Term Loan Due 6/15/2024 [Member] | Secured Debt [Member]
Reorganization [Line Items]
Interest rate					6.00%	5.55%
Maturity date					Jun. 15, 2024
Principal Outstanding					$ 1,694,000,000	$ 1,699,000,000
Second Lien Notes Due 4/1/2026 [Member] | Secured Debt [Member]
Reorganization [Line Items]
Interest rate					8.50%	8.50%
Maturity date					Apr. 01, 2026
Principal Outstanding					$ 1,600,000,000	$ 1,600,000,000
DIP Revolving Facility [Member]
Reorganization [Line Items]
DIP, Maximum line of credit			$ 625,000,000	$ 460,000,000
Debenture Due 11/15/2031 [Member] | Secured Subsidiary Debt [Member]
Reorganization [Line Items]
Interest rate					8.50%	8.50%
Maturity date					Nov. 15, 2031
Principal Outstanding					$ 100,000,000	$ 100,000,000
Debenture Due 5/15/2027 [Member] | Unsecured Subsidiary Debt [Member]
Reorganization [Line Items]
Interest rate					6.75%	6.75%
Maturity date					May 15, 2027
Principal Outstanding					$ 200,000,000	$ 200,000,000
Debenture Due 2/1/2028 [Member] | Unsecured Subsidiary Debt [Member]
Reorganization [Line Items]
Interest rate					6.86%	6.86%
Maturity date					Feb. 01, 2028
Principal Outstanding					$ 300,000,000	$ 300,000,000
Debenture Due 2/15/2028 [Member] | Unsecured Subsidiary Debt [Member]
Reorganization [Line Items]
Interest rate					6.73%	6.73%
Maturity date					Feb. 15, 2028
Principal Outstanding					$ 200,000,000	$ 200,000,000
Debenture Due 10/15/2029 [Member] | Unsecured Subsidiary Debt [Member]
Reorganization [Line Items]
Interest rate					8.40%	8.40%
Maturity date					Oct. 15, 2029
Principal Outstanding					$ 50,000,000	$ 50,000,000
New First Lien Notes [Member]
Reorganization [Line Items]
Maturity date					Oct. 15, 2027
Subsequent Event [Member] | DIP Revolving Facility [Member]
Reorganization [Line Items]
DIP, Maximum line of credit	$ 625,000,000
Subsequent Event [Member] | DIP Term Loan Facility [Member]
Reorganization [Line Items]
DIP, Maximum line of credit	$ 500,000,000
Subsequent Event [Member] | New First Lien Notes [Member]
Reorganization [Line Items]
Interest rate	5.875%
Maturity date	Oct. 15, 2027
Principal Outstanding	$ 1,150,000,000
Maximum [Member]
Reorganization [Line Items]
Maturity period		8 years
Maximum [Member] | Secured Debt [Member]
Reorganization [Line Items]
Reorganization plan, Interest rate		2.50%
Maximum [Member] | Unsecured Debt [Member]
Reorganization [Line Items]
Reorganization plan, Interest rate		3.50%
Minimum [Member]
Reorganization [Line Items]
Maturity period		1 year
Percentage of debt held by the Consenting Noteholders		50.10%