DEBT AND CREDIT AGREEMENTS (Details) (USD $)	Apr. 17, 2013	Mar. 31, 2013	Dec. 31, 2012
Debt
Current Maturities		$ (75,000,000)	$ (75,000,000)
Long-Term Debt, excluding current maturities		1,052,000,000	1,012,000,000
Borrowing base prior to approval	1,700,000,000
Borrowing base	2,300,000,000
7.33% weighted-average fixed rate notes
Debt
Total debt		95,000,000	95,000,000
Current Maturities		(75,000,000)	(75,000,000)
Weighted-average interest rate (as a percent)		7.33%	7.33%
6.51% weighted-average fixed rate notes
Debt
Total debt		425,000,000	425,000,000
Weighted-average interest rate (as a percent)		6.51%	6.51%
9.78% notes
Debt
Total debt		67,000,000	67,000,000
Interest rate (as a percent)		9.78%	9.78%
5.58% weighted-average fixed rate notes
Debt
Total debt		175,000,000	175,000,000
Weighted-average interest rate (as a percent)		5.58%	5.58%
Revolving Credit Facility
Debt
Total debt		365,000,000	325,000,000
Weighted-average interest rate (as a percent)		2.30%
Availability under the credit facility		$ 534,000,000