Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE - Fair Value of Other Financial Instruments (Details)

v3.4.0.3
FAIR VALUE - Fair Value of Other Financial Instruments (Details) - USD ($)
Mar. 31, 2016
Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt $ 803,121,312 $ 835,290,329
Debt instrument, unamortized discount 2,100,000  
Asset retirement obligations 100,000  
Carrying Amount [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior unsecured notes 686,100,000  
Revolving credit facility 117,000,000  
Estimated Fair Value [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior unsecured notes $ 443,500,000