DEBT (Summary of Debt) (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Short-term Debt [Abstract]
Total short-term debt		$ 0	$ 0	$ 0
Long Term Debt
Total long-term debt including current maturities	[1]	1,979,623	1,984,779	1,984,220
Unamortized discounts and debt issuance cost		(24,821)	(22,716)	(23,893)
Less current maturities		130	150,137	145
Total long-term debt		1,979,493	1,834,642	1,984,075
Total debt	[2]	1,979,623	1,984,779	1,984,220
Estimated fair value of long-term debt		2,191,361	2,092,673	2,237,325
10.125% notes due 2015 [Member]
Long Term Debt
Total long-term debt including current maturities	[3]	150,000	150,000	150,000
6.50% notes due 2016 [Member]
Long Term Debt
Total long-term debt including current maturities		0	125,001	125,001
6.40% notes due 2017 [Member]
Long Term Debt
Total long-term debt including current maturities		0	218,633	218,633
7.00% notes due 2018 [Member]
Long Term Debt
Total long-term debt including current maturities		272,512	400,000	400,000
10.375% notes due 2018 [Member]
Long Term Debt
Total long-term debt including current maturities		250,000	250,000	250,000
7.50% notes due 2021 [Member]
Long Term Debt
Total long-term debt including current maturities		600,000	600,000	600,000
8.85% notes due 2021 [Member]
Long Term Debt
Total long-term debt including current maturities		6,000	6,000	6,000
4.50% notes due 2025 [Member]
Long Term Debt
Total long-term debt including current maturities		400,000	0	0
7.15% notes due 2037 [Member]
Long Term Debt
Total long-term debt including current maturities		240,188	240,188	240,188
Other Notes
Long Term Debt
Total long-term debt including current maturities	[4]	503	637	753
10.125% notes due 2015 and 6.50% notes due 2016 [Member]
Long Term Debt
Unamortized deferred interest rate swap gain	[5]	241	3,036	3,538
Bank line of Credit [Member]
Short-term Debt [Abstract]
Total short-term debt	[4],[6]	0	0	0
Industrial revenue bonds [Member]
Long Term Debt
Total long-term debt including current maturities		0	14,000	14,000
Bank line of Credit [Member]
Long Term Debt
Total long-term debt including current maturities	[4],[6],[7]	$ 85,000	$ 0	$ 0

[1] The debt balances as of December 31, 2014 and September 30, 2014 have been adjusted to reflect our early adoption of ASU 2015-03 and related election as discussed in Note 17.

[2] Face value of our debt is equal to total debt less unamortized discounts and debt issuance costs, and unamortized deferred interest rate swap gain, as follows: September 30, 2015 - $2,004,203 thousand, December 31, 2014 - $2,004,459 thousand and September 30, 2014 - $2,004,575 thousand.

[3] The 10.125% notes due 2015 are classified as long-term debt (not current maturities) as of September 30, 2015 due to our intent and ability to refinance these notes at maturity (December 15, 2015) using our line of credit.

[4] Non-publicly traded debt.

[5] The unamortized deferred gain was realized upon the August 2011 settlement of interest rate swaps as discussed in Note 6.

[6] Borrowings on the bank line of credit are classified as short-term debt if we intend to repay within twelve months and as long-term debt otherwise.

[7] The effective interest rate is the current credit spread over LIBOR.