FAIR VALUE OF FINANCIAL INSTRUMENTS (Debt) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Estimate Of Fair Value Fair Value Disclosure [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long Term Debt Fair Value	$ 1,010,489	$ 901,893
Estimate Of Fair Value Fair Value Disclosure [Member] | Industrial Revenue Bond [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long Term Debt Fair Value	8,400	8,400
Estimate Of Fair Value Fair Value Disclosure [Member] | RevolvingCreditFacilityMember
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long Term Debt Fair Value	14,000	286,800
Estimate Of Fair Value Fair Value Disclosure [Member] | Senior Notes Five Seventy Four [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long Term Debt Fair Value	127,166	128,198
Estimate Of Fair Value Fair Value Disclosure [Member] | Senior Notes Five Fifty One [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long Term Debt Fair Value	167,607	168,491
Estimate Of Fair Value Fair Value Disclosure [Member] | Senior Notes Three Eighty Four [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long Term Debt Fair Value	100,323	100,677
Estimate Of Fair Value Fair Value Disclosure [Member] | Senior Notes Three Seventy [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long Term Debt Fair Value	227,803	0
Estimate Of Fair Value Fair Value Disclosure [Member] | Senior Notes Three Eighty Five [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long Term Debt Fair Value	97,764	0
Estimate Of Fair Value Fair Value Disclosure [Member] | Senior Notes Four Twenty Four [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long Term Debt Fair Value	193,462	198,581
Estimate Of Fair Value Fair Value Disclosure [Member] | Senior Notes Four Zero Five [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long Term Debt Fair Value	72,501	0
Estimate Of Fair Value Fair Value Disclosure [Member] | Other Debt Obligations [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long Term Debt Fair Value	1,463	10,746
Carrying Reported Amount Fair Value Disclosure [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	987,920	880,215
Carrying Reported Amount Fair Value Disclosure [Member] | Industrial Revenue Bond [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	8,400	8,400
Carrying Reported Amount Fair Value Disclosure [Member] | RevolvingCreditFacilityMember
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	14,000	286,800
Carrying Reported Amount Fair Value Disclosure [Member] | Senior Notes Five Seventy Four [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	125,007	125,011
Carrying Reported Amount Fair Value Disclosure [Member] | Senior Notes Five Fifty One [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	150,000	150,000
Carrying Reported Amount Fair Value Disclosure [Member] | Senior Notes Three Eighty Four [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	100,323	100,677
Carrying Reported Amount Fair Value Disclosure [Member] | Senior Notes Three Seventy [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	225,000	0
Carrying Reported Amount Fair Value Disclosure [Member] | Senior Notes Three Eighty Five [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	97,764	0
Carrying Reported Amount Fair Value Disclosure [Member] | Senior Notes Four Twenty Four [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	193,462	198,581
Carrying Reported Amount Fair Value Disclosure [Member] | Senior Notes Four Zero Five [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	72,501	0
Carrying Reported Amount Fair Value Disclosure [Member] | Other Debt Obligations [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	$ 1,463	$ 10,746