Long-Term Debt (Schedule Of Unsecured Debt) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 15, 2019	Mar. 19, 2018
Debt Instrument [Line Items]
Principal Outstanding	$ 17,516	$ 17,400
Term Loan Due 06/15/2024 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jun. 15, 2024
Secured Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 5,711	5,246
Secured Debt [Member] | Term Loan Due 3/31/20121 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Mar. 31, 2021
Principal Outstanding		$ 1,402
Total debt weighted average of stated interest rate.		5.28%
Secured Debt [Member] | Term Loan Due 10/12/20121 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Oct. 12, 2021
Principal Outstanding		$ 239
Total debt weighted average of stated interest rate.		7.405%
Secured Debt [Member] | Revolver Due 2/27/2024 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Feb. 27, 2024
Principal Outstanding	$ 749	$ 275
Total debt weighted average of stated interest rate.	4.76%	5.28%
Secured Debt [Member] | Term Loan Due 06/15/2024 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jun. 15, 2024
Principal Outstanding	$ 1,699	$ 1,716
Total debt weighted average of stated interest rate.	5.55%	6.28%
Secured Debt [Member] | First Lien Notes Due 4/1/2027 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Apr. 01, 2027
Principal Outstanding	$ 1,650
Total debt weighted average of stated interest rate.	8.00%			8.00%
Secured Debt [Member] | Second Lien Notes Due 4/1/2026 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Apr. 01, 2026
Principal Outstanding	$ 1,600	$ 1,600
Total debt weighted average of stated interest rate.	8.50%	8.50%			8.50%
Secured Debt [Member] | IDRB due 5/1/2030 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	May 01, 2030
Principal Outstanding	$ 13	$ 13
Total debt weighted average of stated interest rate.	6.20%	6.20%
Secured Debt [Member] | Equipment Financings [Member]
Debt Instrument [Line Items]
Principal Outstanding		$ 1
Total debt weighted average of stated interest rate.		0.00%
Unsecured Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 10,949	$ 11,297
Unsecured Debt [Member] | Senior Notes Due 10/1/2018 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Oct. 01, 2018
Total debt weighted average of stated interest rate.		8.125%
Unsecured Debt [Member] | Senior Note Due 3/15/2019 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Mar. 15, 2019	Mar. 15, 2019
Principal Outstanding		$ 348
Total debt weighted average of stated interest rate.		7.125%
Unsecured Debt [Member] | Senior Note Due 4/15/2020 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Apr. 15, 2020
Principal Outstanding	$ 172	$ 172
Total debt weighted average of stated interest rate.	8.50%	8.50%
Unsecured Debt [Member] | Senior Note Due 9/15/2020 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Sep. 15, 2020	Sep. 15, 2020
Principal Outstanding	$ 55	$ 55
Total debt weighted average of stated interest rate.	8.875%	8.875%
Unsecured Debt [Member] | Senior Note Due 7/1/2021 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jul. 01, 2021	Jul. 01, 2021
Principal Outstanding	$ 89	$ 89
Total debt weighted average of stated interest rate.	9.25%	9.25%
Unsecured Debt [Member] | Senior Note Due 9/15/2021 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Sep. 15, 2021	Sep. 15, 2021
Principal Outstanding	$ 220	$ 220
Total debt weighted average of stated interest rate.	6.25%	6.25%
Unsecured Debt [Member] | Senior Note Due 4/15/2022 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Apr. 15, 2022
Principal Outstanding	$ 500	$ 500
Total debt weighted average of stated interest rate.	8.75%	8.75%
Unsecured Debt [Member] | Senior Note Due 9/15/2022 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Sep. 15, 2022
Principal Outstanding	$ 2,188	$ 2,188
Total debt weighted average of stated interest rate.	10.50%	10.50%
Unsecured Debt [Member] | Senior Note Due 1/15/2023 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jan. 15, 2023
Principal Outstanding	$ 850	$ 850
Total debt weighted average of stated interest rate.	7.125%	7.125%
Unsecured Debt [Member] | Senior Note Due 4/15/2024 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Apr. 15, 2024
Principal Outstanding	$ 750	$ 750
Total debt weighted average of stated interest rate.	7.625%	7.625%
Unsecured Debt [Member] | Senior Note Due 1/15/2025 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jan. 15, 2025
Principal Outstanding	$ 775	$ 775
Total debt weighted average of stated interest rate.	6.875%	6.875%
Unsecured Debt [Member] | Senior Note Due 9/15/2025 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Sep. 15, 2025
Principal Outstanding	$ 3,600	$ 3,600
Total debt weighted average of stated interest rate.	11.00%	11.00%
Unsecured Debt [Member] | Debentures Due 11/1/2025 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Nov. 01, 2025
Principal Outstanding	$ 138	$ 138
Total debt weighted average of stated interest rate.	7.00%	7.00%
Unsecured Debt [Member] | Debentures Due 8/15/2026 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Aug. 15, 2026
Principal Outstanding	$ 2	$ 2
Total debt weighted average of stated interest rate.	6.80%	6.80%
Unsecured Debt [Member] | Senior Note Due 1/15/2027 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jan. 15, 2027
Principal Outstanding	$ 346	$ 346
Total debt weighted average of stated interest rate.	7.875%	7.875%
Unsecured Debt [Member] | Senior Note Due 8/15/2031 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Aug. 15, 2031
Principal Outstanding	$ 945	$ 945
Total debt weighted average of stated interest rate.	9.00%	9.00%
Unsecured Debt [Member] | Debentures Due 10/1/2034 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Oct. 01, 2034
Principal Outstanding	$ 1	$ 1
Total debt weighted average of stated interest rate.	7.68%	7.68%
Unsecured Debt [Member] | Debentures Due 7/1/2035 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jul. 01, 2035
Principal Outstanding	$ 125	$ 125
Total debt weighted average of stated interest rate.	7.45%	7.45%
Unsecured Debt [Member] | Debentures Due 10/1/2046 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Oct. 01, 2046
Principal Outstanding	$ 193	$ 193
Total debt weighted average of stated interest rate.	7.05%	7.05%
Secured Subsidiary Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 106	$ 107
Secured Subsidiary Debt [Member] | Debentures Due 11/15/2031 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Nov. 15, 2031
Principal Outstanding	$ 100	$ 100
Total debt weighted average of stated interest rate.	8.50%	8.50%
Secured Subsidiary Debt [Member] | RUS Loan Contracts Due 1/3/2028 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jan. 03, 2028
Principal Outstanding	$ 6	$ 7
Total debt weighted average of stated interest rate.	6.154%	6.154%
Unsecured Subsidiary Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 750	$ 750
Unsecured Subsidiary Debt [Member] | Debentures Due 5/15/2027
Debt Instrument [Line Items]
Debt instrument, maturity date	May 15, 2027
Principal Outstanding	$ 200	$ 200
Total debt weighted average of stated interest rate.	6.75%	6.75%
Unsecured Subsidiary Debt [Member] | Debentures Due 2/1/2028 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Feb. 01, 2028
Principal Outstanding	$ 300	$ 300
Total debt weighted average of stated interest rate.	6.86%	6.86%
Unsecured Subsidiary Debt [Member] | Debentures Due 2/15/2028 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Feb. 15, 2028
Principal Outstanding	$ 200	$ 200
Total debt weighted average of stated interest rate.	6.73%	6.73%
Unsecured Subsidiary Debt [Member] | Debentures Due 10/15/2029 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Oct. 15, 2029
Principal Outstanding	$ 50	$ 50
Total debt weighted average of stated interest rate.	8.40%	8.40%
Senior Unsecured Debt [Member] | Senior Note Due 3/15/2019 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Mar. 15, 2019
Total debt weighted average of stated interest rate.	7.125%		7.125%
Senior Unsecured Debt [Member] | Senior Note Due 4/15/2020 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Apr. 15, 2020
Total debt weighted average of stated interest rate.			8.50%
Senior Unsecured Debt [Member] | Senior Note Due 9/15/2020 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Sep. 15, 2020
Total debt weighted average of stated interest rate.			8.875%
Senior Unsecured Debt [Member] | Senior Note Due 7/1/2021 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date			Jul. 01, 2021
Total debt weighted average of stated interest rate.			9.25%
Senior Secured Debt, Senior Unsecured Debt And Subsidiary Debentures [Member]
Debt Instrument [Line Items]
Principal Outstanding	$ 17,516	$ 17,400
Total debt weighted average of stated interest rate.	8.486%	8.411%
JP Morgan Term Loan B [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jun. 15, 2024