Debt (New Revolver) (Detail) - New Revolver - USD ($)
3 Months Ended
Mar. 21, 2017
Mar. 31, 2017
Apr. 03, 2017
Line Of Credit Facility [Line Items]      
Borrowing base amount   $ 400,000,000  
Debt instrument maturity date   Mar. 21, 2021  
Initial borrowing base amount   $ 225,000,000  
Debt instrument redetermination date   May 01, 2018  
Availability under the facility   $ 104,172,000  
Commitment fee on unused portion of the borrowing base   0.50%  
Letter of Credit      
Line Of Credit Facility [Line Items]      
Basis spread on variable rate   0.125%  
Alternate Base Rate      
Line Of Credit Facility [Line Items]      
Additional interest rate on outstanding amounts in event of default   2.00%  
Outstanding borrowings, accruing interest rate   6.50%  
Alternate Base Rate | Minimum      
Line Of Credit Facility [Line Items]      
Basis spread on variable rate   2.00%  
Alternate Base Rate | Maximum      
Line Of Credit Facility [Line Items]      
Basis spread on variable rate   3.00%  
Adjusted LIBO Rate      
Line Of Credit Facility [Line Items]      
One month interest period   1 month  
Two month interest period   2 months  
Three month interest period   3 months  
Six month interest period   6 months  
Adjusted LIBO Rate | Minimum      
Line Of Credit Facility [Line Items]      
Basis spread on variable rate   3.00%  
Adjusted LIBO Rate | Maximum      
Line Of Credit Facility [Line Items]      
Basis spread on variable rate   4.00%  
Subsequent Event | Adjusted LIBO Rate      
Line Of Credit Facility [Line Items]      
Outstanding borrowings, accruing interest rate     4.53%
Existing Credit Facility      
Line Of Credit Facility [Line Items]      
Borrowing base amount $ 400,000,000    
Debt instrument maturity date Mar. 21, 2021    
Initial borrowing base amount $ 225,000,000    
Debt instrument redetermination date May 01, 2018    
Availability under the facility $ 104,172,000    
Commitment fee on unused portion of the borrowing base 0.50%    
Number of days to make election to eliminate borrowings in excess of borrowing base as the result of a redetermination 10 days    
Existing Credit Facility | Letter of Credit      
Line Of Credit Facility [Line Items]      
Basis spread on variable rate 0.125%    
Existing Credit Facility | Election One      
Line Of Credit Facility [Line Items]      
Number of days to eliminate borrowings in excess of borrowing base as the result of a redetermination 45 days    
Existing Credit Facility | Election Two      
Line Of Credit Facility [Line Items]      
Number of days to eliminate borrowings in excess of borrowing base as the result of a redetermination 45 days    
Equal monthly installment period to eliminate borrowings in excess of borrowing base as the result of redetermination 6 months    
Existing Credit Facility | Alternate Base Rate      
Line Of Credit Facility [Line Items]      
Additional interest rate on outstanding amounts in event of default 2.00%    
Existing Credit Facility | Alternate Base Rate | Minimum      
Line Of Credit Facility [Line Items]      
Basis spread on variable rate 2.00%    
Existing Credit Facility | Alternate Base Rate | Maximum      
Line Of Credit Facility [Line Items]      
Basis spread on variable rate 3.00%    
Existing Credit Facility | Adjusted LIBO Rate      
Line Of Credit Facility [Line Items]      
One month interest period 1 month    
Two month interest period 2 months    
Three month interest period 3 months    
Six month interest period 6 months    
Existing Credit Facility | Adjusted LIBO Rate | Minimum      
Line Of Credit Facility [Line Items]      
Basis spread on variable rate 3.00%    
Existing Credit Facility | Adjusted LIBO Rate | Maximum      
Line Of Credit Facility [Line Items]      
Basis spread on variable rate 4.00%