DEBT (Summary of Debt) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012		Jun. 30, 2012
Debt Instrument [Line Items]
Total short-term debt	$ 100,000		$ 0		$ 0
Long Term Debt
Total long-term debt including current maturities	2,524,581		2,677,003		2,813,539
Less current maturities	161		150,602		285,152
Total long-term debt	2,524,420		2,526,401		2,528,387
Estimated fair value of long-term debt	2,756,202		2,766,835		2,636,409
Line of Credit
Debt Instrument [Line Items]
Total short-term debt	100,000		0		0
5.60% notes due 2012
Long Term Debt
Total long-term debt including current maturities	0	[1]	0	[1]	134,535	[1]
6.30% notes due 2013
Long Term Debt
Total long-term debt including current maturities	0	[2]	140,413	[2]	140,382	[2]
10.125% notes due 2015
Long Term Debt
Total long-term debt including current maturities	152,317	[3]	152,718	[3]	153,100	[3]
6.50% notes due 2016
Long Term Debt
Total long-term debt including current maturities	513,369	[4]	515,060	[4]	516,701	[4]
6.40% notes due 2017
Long Term Debt
Total long-term debt including current maturities	349,897	[5]	349,888	[5]	349,878	[5]
7.00% notes due 2018
Long Term Debt
Total long-term debt including current maturities	399,751	[6]	399,731	[6]	399,711	[6]
10.375% notes due 2018
Long Term Debt
Total long-term debt including current maturities	248,757	[7]	248,676	[7]	248,599	[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	239,557	[9]	239,553	[9]	239,549	[9]
Medium-term Notes
Long Term Debt
Total long-term debt including current maturities	6,000		16,000		16,000
Municipal 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	$ 933		$ 964		$ 1,084

[1] Includes decreases for unamortized discounts, as follows: June 30, 2012 — $22 thousand.

[2] Includes decreases for unamortized discounts, as follows: December 31, 2012 — $30 thousand and June 30, 2012 — $62 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: June 30, 2013 — $2,543 thousand, December 31, 2012 — $2,983 thousand and June 30, 2012 — $3,402 thousand. Additionally, includes decreases for unamortized discounts, as follows: June 30, 2013 — $226 thousand, December 31, 2012 — $265 thousand and June 30, 2012 — $302 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: June 30, 2013 — $13,369 thousand, December 31, 2012 — $15,060 thousand and June 30, 2012 — $16,701 thousand. The effective interest rate for these notes is 6.02%.

[5] Includes decreases for unamortized discounts, as follows: June 30, 2013 — $103 thousand, December 31, 2012 —$112 thousand and June 30, 2012 — $122 thousand. The effective interest rate for these notes is 7.41%.

[6] Includes decreases for unamortized discounts, as follows: June 30, 2013 — $249 thousand, December 31, 2012 — $269 thousand and June 30, 2012 — $289 thousand. The effective interest rate for these notes is 7.87%.

[7] Includes decreases for unamortized discounts, as follows: June 30, 2013 — $1,243 thousand, December 31, 2012 — $1,324 thousand and June 30, 2012 — $1,401 thousand. The effective interest rate for these notes is 10.62%.8. The effective interest rate for these notes is 7.75%.

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

[9] Includes decreases for unamortized discounts, as follows: June 30, 2013 — $631 thousand, December 31, 2012 —$635 thousand and June 30, 2012 — $639 thousand. The effective interest rate for these notes is 8.05%.