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Fair Value Measurements (Schedule Of Carrying Values And Estimated Fair Values Of Debt Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Apr. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT		$ 544.8
LIABILITIES SUBJECT TO COMPROMISE	$ 0.0	0.0	$ 7,313.7
LONG-TERM DEBT	545.1		0.0
Long-term Debt, Fair Value		$ 544.8
Debt Instrument, Convertible, Carrying Amount of Equity Component			220.0
Letters of credit outstanding, amount	151.1
Revolving Credit Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Letters of credit outstanding, amount			27.0
Line of Credit | Revolving Credit Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Letters of credit outstanding, amount	19.5
Line of Credit | Letter of Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Letters of credit outstanding, amount	$ 29.9
6.875% Senior Notes, Due August 15, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	6.875%
Four Point Seven Zero Percent Senior Notes Member
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	4.70%
4.875% Senior Notes Due 2022 Member [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	4.875%
Three percent exchangeable senior notes due twenty twenty four [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	3.00%
Four Point Five Percent Senior Notes Member [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	4.50%
4.75% Senior Notes Due 2024 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	4.75%
8.00% senior notes due 2024 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	8.00%
Five Point Two Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	5.20%
7.38% Senior Notes Due 2025 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	7.375%
Seven Point Seven Five Percent Senior Notes Due Two Thousand Twenty Six [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	7.75%
Seven Point Two Zero Percent Debentures Member
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	7.20%
Seven Point Eight Seven Five Percent Senior Notes Member
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	7.875%
5.40% Senior Notes Due 2042 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	5.40%
5.75% Senior notes due 2044
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	5.75%
5.85% Senior Notes Due 2044 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	5.85%
Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	$ 545.1		7,096.3
LIABILITIES SUBJECT TO COMPROMISE	0.0		7,096.3
LONG-TERM DEBT	545.1		0.0
Reported Value Measurement [Member] | Line of Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		581.0
Reported Value Measurement [Member] | Eight Point Two Five Percent Senior Lien Notes Due Two Thousand Twenty Eight Member | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	545.1		0.0
Reported Value Measurement [Member] | 6.875% Senior Notes, Due August 15, 2020 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		122.9
Reported Value Measurement [Member] | Four Point Seven Zero Percent Senior Notes Member | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		100.7
Reported Value Measurement [Member] | 4.875% Senior Notes Due 2022 Member [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		620.8
Reported Value Measurement [Member] | Three percent exchangeable senior notes due twenty twenty four [Member] | Convertible Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		849.5
Reported Value Measurement [Member] | Four Point Five Percent Senior Notes Member [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		303.4
Reported Value Measurement [Member] | 4.75% Senior Notes Due 2024 [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		318.6
Reported Value Measurement [Member] | 8.00% senior notes due 2024 [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		292.3
Reported Value Measurement [Member] | Five Point Two Percent Senior Notes [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		333.7
Reported Value Measurement [Member] | 7.38% Senior Notes Due 2025 [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		360.8
Reported Value Measurement [Member] | Seven Point Seven Five Percent Senior Notes Due Two Thousand Twenty Six [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		1,000.0
Reported Value Measurement [Member] | Seven Point Two Zero Percent Debentures Member | Debentures Due2027 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		112.1
Reported Value Measurement [Member] | Seven Point Eight Seven Five Percent Senior Notes Member | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		300.0
Reported Value Measurement [Member] | 5.40% Senior Notes Due 2042 [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		400.0
Reported Value Measurement [Member] | 5.75% Senior notes due 2044 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		1,000.5
Reported Value Measurement [Member] | 5.85% Senior Notes Due 2044 [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LONG-TERM DEBT	0.0		400.0
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	570.8		940.8
LIABILITIES SUBJECT TO COMPROMISE	0.0		940.8
Long-term Debt, Fair Value	570.8		0.0
Estimate of Fair Value Measurement [Member] | Line of Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		581.0
Estimate of Fair Value Measurement [Member] | Notes Receivable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	244.2
Estimate of Fair Value Measurement [Member] | Eight Point Two Five Percent Senior Lien Notes Due Two Thousand Twenty Eight Member | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	570.8		0.0
Estimate of Fair Value Measurement [Member] | 6.875% Senior Notes, Due August 15, 2020 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		8.6
Estimate of Fair Value Measurement [Member] | Four Point Seven Zero Percent Senior Notes Member | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		4.5
Estimate of Fair Value Measurement [Member] | 4.875% Senior Notes Due 2022 Member [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		32.9
Estimate of Fair Value Measurement [Member] | Three percent exchangeable senior notes due twenty twenty four [Member] | Convertible Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		76.5
Estimate of Fair Value Measurement [Member] | Four Point Five Percent Senior Notes Member [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		13.7
Estimate of Fair Value Measurement [Member] | 4.75% Senior Notes Due 2024 [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		18.8
Estimate of Fair Value Measurement [Member] | 8.00% senior notes due 2024 [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		12.9
Estimate of Fair Value Measurement [Member] | Five Point Two Percent Senior Notes [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		12.7
Estimate of Fair Value Measurement [Member] | 7.38% Senior Notes Due 2025 [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		20.9
Estimate of Fair Value Measurement [Member] | Seven Point Seven Five Percent Senior Notes Due Two Thousand Twenty Six [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		44.0
Estimate of Fair Value Measurement [Member] | Seven Point Two Zero Percent Debentures Member | Debentures Due2027 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		5.7
Estimate of Fair Value Measurement [Member] | Seven Point Eight Seven Five Percent Senior Notes Member | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		21.0
Estimate of Fair Value Measurement [Member] | 5.40% Senior Notes Due 2042 [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		23.6
Estimate of Fair Value Measurement [Member] | 5.75% Senior notes due 2044 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0		38.0
Estimate of Fair Value Measurement [Member] | 5.85% Senior Notes Due 2044 [Member] | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	$ 0.0		$ 26.0

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