DEBT (Summary of Debt) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
Long Term Debt
Long-term Debt, Total	$ 2,006,953		$ 2,522,413		$ 2,666,024
Less current maturities	171		170		140,604
Total long-term debt	2,006,782		2,522,243		2,525,420
Estimated fair value of long-term debt	2,313,964		2,820,399		2,851,237
6.30% notes due 2013
Long Term Debt
Long-term Debt, Total	0	[1]	0	[1]	140,430	[1]
10.125% notes due 2015
Long Term Debt
Long-term Debt, Total	151,674	[2]	151,897	[2]	152,520	[2]
6.50% notes due 2016
Long Term Debt
Long-term Debt, Total	127,678	[3]	511,627	[3]	514,221	[3]
6.40% notes due 2017
Long Term Debt
Long-term Debt, Total	218,578	[4]	349,907	[4]	349,892	[4]
7.00% notes due 2018
Long Term Debt
Long-term Debt, Total	399,783	[5]	399,772	[5]	399,741	[5]
10.375% notes due 2018
Long Term Debt
Long-term Debt, Total	248,888	[6]	248,843	[6]	248,716	[6]
7.50% notes due 2021
Long Term Debt
Long-term Debt, Total	600,000	[7]	600,000	[7]	600,000	[7]
7.15% notes due 2037
Long Term Debt
Long-term Debt, Total	239,564	[8]	239,561	[8]	239,555	[8]
Medium-term Notes
Long Term Debt
Long-term Debt, Total	6,000		6,000		6,000
Industrial revenue bonds
Long Term Debt
Long-term Debt, Total	14,000		14,000		14,000
Other Notes
Long Term Debt
Long-term Debt, Total	$ 788		$ 806		$ 949

[1] Includes decreases for unamortized discounts, as follows: March 31, 2013 — $14 thousand.

[2] Includes an increase for the unamortized portion of the deferred gain realized upon the August 2011 settlement of interest rate swaps, as follows: March 31, 2014 — $1,837 thousand, December 31, 2013 — $2,082 thousand and March 31, 2013 — $2,766 thousand. Additionally, includes decreases for unamortized discounts, as follows: March 31, 2014 — $163 thousand, December 31, 2013 — $185 thousand and March 31, 2013 — $246 thousand. The effective interest rate for these notes is 9.58%.

[3] Includes an increase for the unamortized portion of the deferred gain realized upon the August 2011 settlement of interest rate swaps, as follows: March 31, 2014 — $2,677 thousand, December 31, 2013 — $11,627 thousand and March 31, 2013 — $14,221 thousand. The effective interest rate for these notes is 6.00%.

[4] Includes decreases for unamortized discounts, as follows: March 31, 2014 — $55 thousand, December 31, 2013 — $93 thousand and March 31, 2013 — $108 thousand. The effective interest rate for these notes is 7.41%.

[5] Includes decreases for unamortized discounts, as follows: March 31, 2014 — $217 thousand, December 31, 2013 — $228 thousand and March 31, 2013 — $259 thousand. The effective interest rate for these notes is 7.87%.

[6] Includes decreases for unamortized discounts, as follows: March 31, 2014 — $1,112 thousand, December 31, 2013 — $1,157 thousand and March 31, 2013 — $1,284 thousand. The effective interest rate for these notes is 10.63%.

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

[8] Includes decreases for unamortized discounts, as follows: March 31, 2014 — $624 thousand, December 31, 2013 — $627 thousand and March 31, 2013 — $633 thousand. The effective interest rate for these notes is 8.05%.