DEBT (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended		1 Months Ended
	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Apr. 30, 2015	Jun. 30, 2011	May 31, 2015
Debt Instrument [Line Items]
Debt issued, amount						$ 500,000,000
Interest rate						6.50%
Debt purchased, amount	506,366,000		506,366,000
Total consideration paid for debt	579,659,000	145,918,000	579,676,000
Premium paid for purchase of debt	71,829,000		71,829,000
Transaction cost related to termination of debt			1,464,000
Other cost (benefit) related to debt purchase			(344,000)
Cost of debt purchase		21,734,000	72,949,000
Debt to EBITDA ratio		3.5
EBITDA to net cash interest expense ratio		3.0
Borrowing capacity		446,528,000		446,528,000
Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Applicable margin for LIBOR based borrowing		0.175%
Commitment fee		0.25%
Minimum [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Commitment fee		0.25%
Maximum [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Commitment fee		0.40%
4.50% notes due 2025 [Member]
Debt Instrument [Line Items]
Debt issued, amount		400,000,000		400,000,000
Interest rate		4.50%		4.50%
Debt issued, net proceeds		395,207,000
Maturity year		2025
6.40% notes due 2017 [Member]
Debt Instrument [Line Items]
Interest rate	6.40%	6.40%	6.40%	6.40%
Maturity year		2017	2017
Debt purchased, amount	131,367,000		131,367,000
6.50% notes due 2016 [Member]
Debt Instrument [Line Items]
Interest rate	6.50%	6.50%	6.50%	6.50%
Maturity year		2016	2016
Debt purchased, amount	374,999,000		374,999,000
8.85% notes due 2021 [Member]
Debt Instrument [Line Items]
Interest rate		8.85%		8.85%
Maturity year		2021
Industrial revenue bonds [Member]
Debt Instrument [Line Items]
Maturity year		2022
7.00% notes due 2018 [Member]
Debt Instrument [Line Items]
Interest rate		7.00%		7.00%
Maturity year		2018		2018
Debt purchased, amount		127,303,000		127,303,000
Total consideration paid for debt		145,899,000
Premium paid for purchase of debt		18,140,000		18,140,000
Transaction cost related to termination of debt		456,000
Other cost (benefit) related to debt purchase		(3,138,000)
Cost of debt purchase		21,734,000
Subsequent Event [Member]
Debt Instrument [Line Items]
Debt purchased, amount					343,819,000
Total consideration paid for debt					384,990,000
Premium paid for purchase of debt					41,153,000
Transaction cost related to termination of debt					18,000
Subsequent Event [Member] | 6.40% notes due 2017 [Member]
Debt Instrument [Line Items]
Interest rate					6.40%
Debt purchased, redemption date		Apr. 09, 2015
Maturity year					2017
Debt purchased, amount					218,633,000
Subsequent Event [Member] | 6.50% notes due 2016 [Member]
Debt Instrument [Line Items]
Interest rate					6.50%
Debt purchased, redemption date		Apr. 16, 2015
Maturity year					2016
Debt purchased, amount					125,001,000
Subsequent Event [Member] | 7.00% notes due 2018 [Member]
Debt Instrument [Line Items]
Interest rate					7.00%
Maturity year					2018
Debt purchased, amount					185,000
Bank line of Credit [Member]
Debt Instrument [Line Items]
Amount of bank credit facility	500,000,000	500,000,000	500,000,000	500,000,000
Applicable margin for LIBOR based borrowing		1.50%
Bank line of Credit [Member] | Scenario, Forecast [Member]
Debt Instrument [Line Items]
Amount of bank credit facility							$ 750,000,000
Bank line of Credit [Member] | Minimum [Member]
Debt Instrument [Line Items]
Applicable margin for LIBOR based borrowing		1.50%
Bank line of Credit [Member] | Maximum [Member]
Debt Instrument [Line Items]
Applicable margin for LIBOR based borrowing		2.25%