DEBT (Summary of Debt) (Details) - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Short-term Debt [Abstract]
Total short-term debt		$ 138,500	$ 0	$ 0
Long Term Debt
Total long-term debt including current maturities	[1]	1,907,861	1,984,779	1,983,477
Unamortized discounts and debt issuance cost		(25,975)	(22,716)	(25,146)
Less current maturities		14,124	150,137	158
Total long-term debt		1,893,737	1,834,642	1,983,319
Estimated fair value of long-term debt		2,140,942	2,092,673	2,289,118
10.125% notes due 2015 [Member]
Long Term Debt
Total long-term debt including current maturities	[2]	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	[3]	613	637	769
10.125% notes due 2015 and 6.50% notes due 2016 [Member]
Long Term Debt
Unamortized deferred interest rate swap gain	[4]	523	3,036	4,032
Bank line of Credit [Member]
Short-term Debt [Abstract]
Total short-term debt	[5]	138,500	0	0
Industrial revenue bonds [Member]
Long Term Debt
Total long-term debt including current maturities	[6]	$ 14,000	$ 14,000	$ 14,000

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

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

[3] Non-publicly traded debt.

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

[5] Borrowings are shown as short-term due to our intent to repay within twelve months. The effective interest rate reflects the margin added to LIBOR for LIBOR-based borrowings. We also pay fees for unused borrowing capacity and standby letters of credit.

[6] As of June 30, 2015, we had initiated prepayment; as such, this debt is classified as current maturities of long-term debt.