DEBT (Summary of Debt) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012
Long Term Debt
Total long-term debt including current maturities	$ 2,523,552		$ 2,677,003		$ 2,812,603
Less current maturities	163		150,602		285,153
Total long-term debt	2,523,389		2,526,401		2,527,450
Estimated fair value of long-term debt	2,795,661		2,766,835		2,796,358
5.60% notes due 2012
Long Term Debt
Total long-term debt including current maturities	0	[1]	0	[1]	134,548	[1]
6.30% notes due 2013
Long Term Debt
Total long-term debt including current maturities	0	[2]	140,413	[2]	140,398	[2]
10.125% notes due 2015
Long Term Debt
Total long-term debt including current maturities	152,110	[3]	152,718	[3]	152,911	[3]
6.50% notes due 2016
Long Term Debt
Total long-term debt including current maturities	512,505	[4]	515,060	[4]	515,887	[4]
6.40% notes due 2017
Long Term Debt
Total long-term debt including current maturities	349,902	[5]	349,888	[5]	349,883	[5]
7.00% notes due 2018
Long Term Debt
Total long-term debt including current maturities	399,761	[6]	399,731	[6]	399,721	[6]
10.375% notes due 2018
Long Term Debt
Total long-term debt including current maturities	248,799	[7]	248,676	[7]	248,637	[7]
7.50% notes due 2021
Long Term Debt
Total long-term debt including current maturities	600,000	[8]	600,000	[8]	600,000	[8]
7.15% notes due 2037
Long Term Debt
Total long-term debt including current maturities	239,559	[9]	239,553	[9]	239,551	[9]
Medium-term Notes
Long Term Debt
Total long-term debt including current maturities	6,000		16,000		16,000
Industrial revenue bonds
Long Term Debt
Total long-term debt including current maturities	14,000		14,000		14,000
Other Notes
Long Term Debt
Total long-term debt including current maturities	$ 916		$ 964		$ 1,067

[1] Includes decreases for unamortized discounts, as follows: September 30, 2012 — $9 thousand.

[2] Includes decreases for unamortized discounts, as follows: December 31, 2012 — $30 thousand and September 30, 2012 — $46 thousand.

[3] Includes an increase for the unamortized portion of the deferred gain realized upon the August 2011 settlement of interest rate swaps, as follows: September 30, 2013 — $2,315 thousand, December 31, 2012 — $2,983 thousand and September 30, 2012 — $3,195 thousand. Additionally, includes decreases for unamortized discounts, as follows: September 30, 2013 — $206 thousand, December 31, 2012 — $265 thousand and September 30, 2012 — $284 thousand. The effective interest rate for these notes is 9.59%.

[4] Includes an increase for the unamortized portion of the deferred gain realized upon the August 2011 settlement of interest rate swaps, as follows: September 30, 2013 — $12,505 thousand, December 31, 2012 — $15,060 thousand and September 30, 2012 — $15,887 thousand. The effective interest rate for these notes is 6.02%.

[5] Includes decreases for unamortized discounts, as follows: September 30, 2013 — $98 thousand, December 31, 2012 — $112 thousand and September 30, 2012 — $117 thousand. The effective interest rate for these notes is 7.41%.

[6] Includes decreases for unamortized discounts, as follows: September 30, 2013 — $239 thousand, December 31, 2012 — $269 thousand and September 30, 2012 — $279 thousand. The effective interest rate for these notes is 7.87%.

[7] Includes decreases for unamortized discounts, as follows: September 30, 2013 — $1,201 thousand, December 31, 2012 — $1,324 thousand and September 30, 2012 — $1,363 thousand. The effective interest rate for these notes is 10.62%.

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

[9] Includes decreases for unamortized discounts, as follows: September 30, 2013 — $629 thousand, December 31, 2012 — $635 thousand and September 30, 2012 — $637 thousand. The effective interest rate for these notes is 8.05%.