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Debt (Early debt retirement) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Oct. 31, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Jun. 30, 2024
Debt
Aggregate principal amount of debt retired				$ 1,697
Aggregate cash payment				1,748
Aggregate net gain		$ 21		161
Repayments of debt			$ 450	$ 2,073
7.25% Senior Notes due November 2025
Debt
Debt instrument interest rate stated percentage		7.25%		7.25%
Aggregate principal amount of debt retired				$ 354
7.50% Senior Notes due January 2026
Debt
Debt instrument interest rate stated percentage		7.50%		7.50%
Aggregate principal amount of debt retired				$ 569
11.50% Senior Guaranteed Notes due January 2027
Debt
Debt instrument interest rate stated percentage		11.50%		11.50%
Aggregate principal amount of debt retired				$ 687
8.00% Senior Notes due February 2027
Debt
Debt instrument interest rate stated percentage		8.00%	8.00%	8.00%	8.00%
Aggregate principal amount of debt retired				$ 87
8.00% Senior Notes due February 2027 \| Subsequent Event
Debt
Debt instrument interest rate stated percentage	8.00%
Repayments of debt	$ 655
8.00% Senior Notes due February 2027 and 6.875% Senior Secured Notes due February 2027. \| Subsequent Event
Debt
Repayments of debt	$ 903
6.875% Senior Secured Notes due February 2027
Debt
Debt instrument interest rate stated percentage			6.875%
6.875% Senior Secured Notes due February 2027 \| Subsequent Event
Debt
Debt instrument interest rate stated percentage	6.875%
Repayments of debt	$ 248
Senior Notes due 7.35% December 2041 and Notes due 7% June 2028 \| Subsequent Event
Debt
Repayments of debt	$ 100
7.35% Senior Notes due December 2041
Debt
Debt instrument interest rate stated percentage			7.35%
7.35% Senior Notes due December 2041 \| Subsequent Event
Debt
Debt instrument interest rate stated percentage	7.35%
Repayments of debt	$ 89
7.00% Notes due June 2028
Debt
Debt instrument interest rate stated percentage			7.00%
7.00% Notes due June 2028 \| Subsequent Event
Debt
Debt instrument interest rate stated percentage	7.00%
Repayments of debt	$ 16
Tendered
Debt
Aggregate principal amount of debt retired				845
Aggregate cash payment				886
Aggregate net gain				144
Tendered \| 7.25% Senior Notes due November 2025
Debt
Aggregate principal amount of debt retired				249
Tendered \| 11.50% Senior Guaranteed Notes due January 2027
Debt
Aggregate principal amount of debt retired				596
Redeemed
Debt
Aggregate principal amount of debt retired				852
Aggregate cash payment				862
Aggregate net gain		$ 21		17
Redeemed \| 7.25% Senior Notes due November 2025
Debt
Aggregate principal amount of debt retired				105
Redeemed \| 7.50% Senior Notes due January 2026
Debt
Aggregate principal amount of debt retired				569
Redeemed \| 11.50% Senior Guaranteed Notes due January 2027
Debt
Aggregate principal amount of debt retired				91
Redeemed \| 8.00% Senior Notes due February 2027
Debt
Aggregate principal amount of debt retired				$ 87