DEBT AND CREDIT AGREEMENTS (Details) (USD $)	Jun. 30, 2013	Apr. 17, 2013	Dec. 31, 2012
Debt
Current Maturities	$ (75,000,000)		$ (75,000,000)
Long-Term Debt, excluding current maturities	1,067,000,000		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	380,000,000		325,000,000
Weighted-average interest rate (as a percent)	2.00%
Availability under the credit facility	519,000,000
Line of credit	$ 900,000,000