Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On A Nonrecurring Basis) (Details) (Fair Value, Measurements, Nonrecurring [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures		$ 160,256
Exempt facility revenue bonds	29,968	27,269
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures		160,256
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Exempt facility revenue bonds	29,968	27,269
1.875% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	166,292
1.875% convertible debentures [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	166,292
1.75% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	302,466
1.75% convertible debentures [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	$ 302,466