Fair Value Measurements (Details Textual) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Debt instrument value
Long term debt, book value	$ 620,000	$ 575,000
8.625 Percent Senior Notes Due 2017 [Member]
Debt instrument value
Long term debt, book value	375,000
Long term debt, Fair Value	386,250	380,625
8.25 Percent Senior Notes Due 2011 [Member]
Debt instrument value
Long term debt, book value	200,000
Long term debt, Fair Value	200,000
6.75 Percent Senior Notes Due 2014 [Member]
Debt instrument value
Long term debt, book value	199,000	200,000
Long term debt, Fair Value	$ 197,000	$ 197,000