Borrowings and Other Obligations (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Jun. 30, 2022	Dec. 31, 2021	Oct. 27, 2021	Aug. 04, 2020	Dec. 12, 2019
Short-term Debt [Line Items]
Debt instrument, unused borrowing capacity, amount		$ 42
Finance Lease, Liability, Current		14	$ 12
Interest Payable, Current		24	35
LC Credit Agreement Letters of Credit
Short-term Debt [Line Items]
Letters of credit outstanding, amount		173
Committed letters of credit
Short-term Debt [Line Items]
Letters of credit outstanding, amount		205
Exit Notes
Short-term Debt [Line Items]
Debt Tender Redemption				$ 1,600
Committed Letters of Credit
Short-term Debt [Line Items]
Letters of credit outstanding, amount		378
Letters of credit outstanding, cash collateral		205
Amended LC Credit Agreement [Member]
Short-term Debt [Line Items]
Credit agreement, maximum capacity						$ 215
Senior Notes 8.625 Percent Due 2030
Short-term Debt [Line Items]
Face amount of debt				$ 1,600
Senior Notes
Short-term Debt [Line Items]
Long-term Debt		300
Senior Notes | Senior Notes 8.75 Percent Due 2024
Short-term Debt [Line Items]
Stated interest rate on debt	8.75%
Repayments of Senior Debt	$ 500
Senior Notes | Exit Notes, 11.00 Percent Due 2024
Short-term Debt [Line Items]
Stated interest rate on debt						11.00%
Senior Notes | Senior Notes 8.625 Percent Due 2030
Short-term Debt [Line Items]
Stated interest rate on debt					8.625%
Long-term Debt		1,585	1,584
Senior Notes | Senior Notes 6.5 Percent Due 2028
Short-term Debt [Line Items]
Stated interest rate on debt					6.50%
Face amount of debt					$ 500
Secured Debt
Short-term Debt [Line Items]
Long-term Debt		$ 489	$ 488