DEBT (Summary of Debt) (Details) - USD ($)		Dec. 31, 2015	Nov. 30, 2015	Jul. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Total short-term debt		$ 0			$ 0
Total long-term debt including current maturities	[1]	1,980,464,000			1,984,779,000
Unamortized discounts and debt issuance costs		(23,734,000)			(22,716,000)
Less current maturities		130,000			150,137,000
Total long-term debt		1,980,334,000			1,834,642,000
Total debt	[2]	1,980,464,000			1,984,779,000
Estimated fair value of long-term debt		2,204,816,000			2,092,673,000
10.125% notes due 2015 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		0	$ 150,000,000		150,000,000
6.50% notes due 2016 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		0			125,001,000
6.40% notes due 2017 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		0			218,633,000
7.00% notes due 2018 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		272,512,000			400,000,000
10.375% notes due 2018 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		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
8.85% notes due 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		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			0
7.15% notes due 2037 [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		240,188,000			240,188,000
10.125% notes due 2015 and 6.50% notes due 2016 [Member]
Debt Instrument [Line Items]
Unamortized deferred interest rate swap gain	[3]	0			3,036,000
Bank Line of Credit [Member]
Debt Instrument [Line Items]
Total short-term debt	[4],[5],[6]	0			0
Bank Line of Credit [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities	[4],[5],[6]	235,000,000			0
Industrial Revenue Bonds [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities		0		$ 14,000,000	14,000,000
Other Notes [Member]
Debt Instrument [Line Items]
Total long-term debt including current maturities	[5]	$ 498,000			$ 637,000

[1] The debt balances as of December 31, 2014 have been adjusted to reflect our early adoption of ASU 2015-03 and related election as discussed in Note 1 under the caption New Accounting Standards.

[2] Face value of our debt is equal to total debt plus unamortized discounts and debt issuance costs, and unamortized deferred interest rate swap gain, as follows: December 31, 2015 - $2,004,198 thousand and December 31, 2014 - $2,004,459 thousand.

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

[4] 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.

[5] Non-publicly traded debt.

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