Fair Value (Carrying Value And Estimated Fair Value Of Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt to affiliated trusts	$ 51,547	$ 51,547
Level 2 [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	962,100	962,100
Level 2 [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,099,091	1,135,536
Level 3 [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	222,000	222,000
Nonrecourse long-term debt	43,165	46,471
Long-term debt to affiliated trusts	51,547	51,547
Level 3 [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	232,748	234,226
Nonrecourse long-term debt	48,227	51,974
Long-term debt to affiliated trusts	$ 43,810	$ 43,810