XML 41 R29.htm IDEA: XBRL DOCUMENT v3.7.0.1
Debt (Details) - USD ($)
3 Months Ended
Mar. 31, 2017
May 03, 2017
Apr. 28, 2017
Feb. 17, 2017
Dec. 31, 2016
Dec. 09, 2016
Apr. 14, 2015
Revolving Credit Agreement (Textual) [Abstract]              
Senior unsecured notes $ 573,968,000       $ 573,924,000    
Deferred loan costs         $ 1,200,000    
Repay deficit in agreement period 6 months            
Third Amended Credit Agreement [Member]              
Revolving Credit Agreement (Textual) [Abstract]              
Amended maximum borrowing capacity $ 500,000,000            
Senior Notes | Senior Notes Due 2023              
Revolving Credit Agreement (Textual) [Abstract]              
Senior unsecured notes $ 575,000,000         $ 175,000,000 $ 400,000,000
Interest rate 6.875%         6.875% 6.875%
Subsequent Event [Member] | Senior Notes | Senior Notes Due 2023              
Revolving Credit Agreement (Textual) [Abstract]              
Senior unsecured notes   $ 575,000,000.0          
Interest rate   6.875%          
Revolving Credit Facility [Member]              
Revolving Credit Agreement (Textual) [Abstract]              
Borrowings under Credit Agreement $ 0            
Maximum borrowing capacity 400,000,000            
Revolving Credit Facility [Member] | Subsequent Event [Member]              
Revolving Credit Agreement (Textual) [Abstract]              
Borrowings under Credit Agreement   $ 0          
Maximum borrowing capacity     $ 450,000,000        
Letter of Credit [Member]              
Revolving Credit Agreement (Textual) [Abstract]              
Outstanding letters of credit $ 800,000            
Letter of Credit [Member] | Subsequent Event [Member]              
Revolving Credit Agreement (Textual) [Abstract]              
Outstanding letters of credit   $ 800,000          
Corporate Joint Venture [Member] | San Mateo Midstream [Member]              
Revolving Credit Agreement (Textual) [Abstract]              
Ownership percentage 51.00%     51.00%