Fair Value (Fair Value And Carrying Value Of Debt Instruments) (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended	3 Months Ended
	Apr. 16, 2012	Mar. 31, 2012		Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Less current portion		$ 57,309		386,255
7.20% Senior Notes, Payable April 15, 2012 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage		7.20%		7.20%
Notes payable, maturity date		Apr. 15, 2012
Company repaid principal amount	336,270	336,300
Debt instruments interest accrued	12,106	12,106
6.125% Notes, Payable January 15, 2016 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate percentage		6.125%
Notes payable, maturity date		Jan. 15, 2016
Five-Year Senior Secured Credit Facility, Due July 8, 2016 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable, maturity date		Jul. 08, 2016
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Industrial revenue bonds, capital leases and other		51,758		52,169
Total long-term debt		1,787,483		1,650,675
Less current portion		57,309		386,591
Long-term debt, less current portion		1,730,174		1,264,084
Fair Value [Member] | 7.20% Senior Notes, Payable April 15, 2012 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable		334,925	[1]	336,606	[1]
Fair Value [Member] | 6.125% Notes, Payable January 15, 2016 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable		989,100		963,900
Fair Value [Member] | Five-Year Senior Secured Credit Facility, Due July 8, 2016 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable		411,700		298,000
Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Industrial revenue bonds, capital leases and other		51,758		52,169
Total long-term debt		1,699,728		1,586,439
Less current portion		57,309		386,255
Long-term debt, less current portion		1,642,419		1,200,184
Carrying Value [Member] | 7.20% Senior Notes, Payable April 15, 2012 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable		336,270	[1]	336,270	[1]
Carrying Value [Member] | 6.125% Notes, Payable January 15, 2016 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable		900,000		900,000
Carrying Value [Member] | Five-Year Senior Secured Credit Facility, Due July 8, 2016 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable		$ 411,700		298,000

[1] On April 16, 2012, the Company repaid the $336,270 principal amount of outstanding senior 7.20% notes, together with accrued interest of $12,106 at maturity using available borrowings under its Senior Credit Facility. As a result, the Company classified the outstanding senior 7.20% notes as long-term debt as of March 31, 2012.