Fair Value Measurements (Details) (USD $)	12 Months Ended
	Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2010
Fair Value Measurements (Textual) [Abstract]
Total Debt		$ 1,073,825,000	$ 1,159,215,000
Impairment charges	6,600,000
Corporate Magic [Member]
Fair Value Measurements (Textual) [Abstract]
Impairment charges	6,600,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair value liabilities measured on recurring basis [Abstract]
Variable to fixed interest rate swaps			12,227,000
Variable to fixed natural gas swaps			226,000
Total liabilities measured at fair value			12,453,000
Fair Value, Inputs, Level 1 [Member]
Fair value liabilities measured on recurring basis [Abstract]
Variable to fixed interest rate swaps			0
Variable to fixed natural gas swaps			0
Total liabilities measured at fair value			0
Fair Value, Inputs, Level 2 [Member]
Fair value liabilities measured on recurring basis [Abstract]
Variable to fixed interest rate swaps			12,227,000
Variable to fixed natural gas swaps			226,000
Total liabilities measured at fair value			12,453,000
Fair Value, Inputs, Level 3 [Member]
Fair value liabilities measured on recurring basis [Abstract]
Variable to fixed interest rate swaps			0
Variable to fixed natural gas swaps			0
Total liabilities measured at fair value			0
Convertible Notes Payable [Member]
Fair Value Measurements (Textual) [Abstract]
Total Debt		319,200,000
Face amount of outstanding debt		360,000,000
Accrued interest on convertible notes		3.75%
Fair value of the convertible notes		338,000,000
Senior Notes [Member]
Fair Value Measurements (Textual) [Abstract]
Total Debt		152,200,000
Accrued interest on convertible notes		6.75%
Fair value of senior notes		152,200,000
Bonds A Series [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes receivables, carrying value		95,400,000
Bonds B Series [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes receivables, carrying value		57,300,000
Notes receivable, fair value		36,000,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair value assets measured on recurring basis [Abstract]
Deferred compensation plan investments		13,892,000	13,422,000
Total assets measured at fair value		13,892,000	13,422,000
Fair Value, Inputs, Level 1 [Member]
Fair value assets measured on recurring basis [Abstract]
Deferred compensation plan investments		13,892,000	13,422,000
Total assets measured at fair value		13,892,000	13,422,000
Fair Value, Inputs, Level 2 [Member]
Fair value assets measured on recurring basis [Abstract]
Deferred compensation plan investments		0	0
Total assets measured at fair value		0	0
Fair Value, Inputs, Level 3 [Member]
Fair value assets measured on recurring basis [Abstract]
Deferred compensation plan investments		0	0
Total assets measured at fair value		$ 0	$ 0