Fair Value Measurements (Details) (6.75% Notes, USD $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Mar. 31, 2015
Dec. 31, 2014
Liabilities:      
Debt instrument, stated interest rate 6.75%    
Fair Value, Inputs, Level 1      
Liabilities:      
Long term debt, Carrying Amount   $ 741,722 $ 742,017
Long term debt, Fair Value   $ 773,588 $ 751,538