DEBT (Summary of Debt) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013		Sep. 30, 2013
Long Term Debt
Long-term Debt, Total	$ 2,006,113	[1]	$ 2,522,413	[1]	$ 2,523,552	[1]
Less current maturities	145	[2]	170	[2]	163	[2]
Total long-term debt	2,005,968		2,522,243		2,523,389
Estimated fair value of long-term debt	2,259,218		2,820,399		2,795,661
10.125% notes due 2015
Long Term Debt
Long-term Debt, Total	151,212	[3]	151,897	[3]	152,110	[3]
6.50% notes due 2016
Long Term Debt
Long-term Debt, Total	127,209	[4]	511,627	[4]	512,505	[4]
6.40% notes due 2017
Long Term Debt
Long-term Debt, Total	218,585	[5]	349,907	[5]	349,902	[5]
7.00% notes due 2018
Long Term Debt
Long-term Debt, Total	399,805	[6]	399,772	[6]	399,761	[6]
10.375% notes due 2018
Long Term Debt
Long-term Debt, Total	248,981	[7]	248,843	[7]	248,799	[7]
7.50% notes due 2021
Long Term Debt
Long-term Debt, Total	600,000	[8]	600,000	[8]	600,000	[8]
7.15% notes due 2037
Long Term Debt
Long-term Debt, Total	239,568	[9]	239,561	[9]	239,559	[9]
Medium-term Notes
Long Term Debt
Long-term Debt, Total	6,000	[1]	6,000	[1]	6,000	[1]
Industrial revenue bonds
Long Term Debt
Long-term Debt, Total	14,000	[2]	14,000	[2]	14,000	[2]
Other Notes
Long Term Debt
Long-term Debt, Total	$ 753	[9]	$ 806	[9]	$ 916	[9]

[1] This note matures in 2021, has a stated interest rate of 8.85% and an effective interest rate of 8.88%.

[2] This variable-rate tax-exempt bond matures in November 2022 and is backed by a standby letter of credit.

[3] Includes an increase for the unamortized deferred gain realized upon the August 2011 settlement of interest rate swaps, as follows: September 30, 2014 — $1,330 thousand, December 31, 2013 — $2,082 thousand and September 30, 2013 — $2,315 thousand. Additionally, includes decreases for unamortized discounts, as follows: September 30, 2014 — $118 thousand, December 31, 2013 — $185 thousand and September 30, 2013 — $206 thousand. The effective interest rate for these notes is 9.58%.

[4] Includes an increase for the unamortized deferred gain realized upon the August 2011 settlement of interest rate swaps, as follows: September 30, 2014 — $2,208 thousand, December 31, 2013 — $11,627 thousand and September 30, 2013 — $12,505 thousand. The effective interest rate for these notes is 6.00%.

[5] Includes decreases for unamortized discounts, as follows: September 30, 2014 — $48 thousand, December 31, 2013 — $93 thousand and September 30, 2013 — $98 thousand. The effective interest rate for these notes is 7.41%.

[6] Includes decreases for unamortized discounts, as follows: September 30, 2014 — $195 thousand, December 31, 2013 — $228 thousand and September 30, 2013 — $239 thousand. The effective interest rate for these notes is 7.87%.

[7] Includes decreases for unamortized discounts, as follows: September 30, 2014 — $1,019 thousand, December 31, 2013 — $1,157 thousand and September 30, 2013 — $1,201 thousand. The effective interest rate for these notes is 10.625%.

[8] The effective interest rate for these notes is 7.75%.

[9] Includes decreases for unamortized discounts, as follows: September 30, 2014 — $620 thousand, December 31, 2013 — $627 thousand and September 30, 2013 — $629 thousand. The effective interest rate for these notes is 8.05%.