DEBT (Summary of Debt) (Details) - USD ($)		Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Debt Instrument [Line Items]
Total short-term debt		$ 0	$ 0	$ 0
Total long-term debt including current maturities	[1]	1,981,556,000	1,980,464,000	2,253,806,000
Unamortized discounts and debt issuance costs		(22,638,000)	(23,734,000)	(25,852,000)
Less current maturities		131,000	130,000	365,441,000
Total long-term debt		1,981,425,000	1,980,334,000	1,888,365,000
Total debt	[2]	1,981,556,000	1,980,464,000	2,253,806,000
Estimated fair value of long-term debt		2,236,669,000	2,204,816,000	2,160,255,000
10.125% notes due 2015 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		0	0	150,000,000
6.50% notes due 2016 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		0	0	125,001,000
6.40% notes due 2017 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		0	0	218,633,000
7.00% notes due 2018 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		272,512,000	272,512,000	272,697,000
10.375% notes due 2018 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		250,000,000	250,000,000	250,000,000
7.50% notes due 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		600,000,000	600,000,000	600,000,000
8.85% notes due 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		6,000,000	6,000,000	6,000,000
4.50% notes due 2025 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		400,000,000	400,000,000	400,000,000
7.15% notes due 2037 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		240,188,000	240,188,000	240,188,000
Other notes [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities	[3]	494,000	498,000	618,000
10.125% notes due 2015 and 6.50% notes due 2016 [Member]
Debt Instrument [Line Items]
Unamortized deferred interest rate swap gain	[4]	0	0	2,521,000
Bank Line of Credit [Member]
Debt Instrument [Line Items]
Total short-term debt	[3],[5],[6]	0	0	0
Bank Line of Credit [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities	[3],[5],[6]	235,000,000	235,000,000	0
Industrial Revenue Bonds [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		0	$ 0	$ 14,000,000
Other Notes [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		$ 494,000

[1] The debt balances as of March 31, 2015 have been adjusted to reflect our early adoption of ASU 2015-03 and related election as discussed in Note 1, caption Reclassifications.

[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: March 31, 2016 - $2,004,194 thousand, December 31, 2015 - $2,004,198 thousand and March 31, 2015 - $2,277,137 thousand.

[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 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.

[6] The effective interest rate is the spread over LIBOR as of the balance sheet dates.