Annual report pursuant to Section 13 and 15(d)

Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)

v3.6.0.2
Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)
Dec. 31, 2016
Dec. 31, 2015
Assets:    
Commodity derivative assets – current $ 0 $ 97,956,000
Liabilities:    
Derivative liabilities, current 12,932,000 0
Derivative liabilities, noncurrent 14,437,000 0
Fair Value, Measurements, Recurring    
Assets:    
Assets of SERP   4,123
Liabilities:    
Deferred compensation – SERP obligation   4,125,000
Fair Value, Measurements, Recurring | Level 1    
Assets:    
Assets of SERP   4,123
Liabilities:    
Deferred compensation – SERP obligation   (4,125,000)
Fair Value, Measurements, Recurring | Level 2    
Assets:    
Assets of SERP   0
Liabilities:    
Deferred compensation – SERP obligation   0
Fair Value, Measurements, Recurring | Level 3    
Assets:    
Assets of SERP   0
Liabilities:    
Deferred compensation – SERP obligation   0
Fair Value, Measurements, Recurring | Commodity contracts    
Assets:    
Commodity derivative assets – current   97,956,000
Liabilities:    
Derivative liabilities, current (12,932,000)  
Derivative liabilities, noncurrent (14,437,000)  
Fair Value, Measurements, Recurring | Commodity contracts | Level 1    
Assets:    
Commodity derivative assets – current   0
Liabilities:    
Derivative liabilities, current 0  
Derivative liabilities, noncurrent 0  
Fair Value, Measurements, Recurring | Commodity contracts | Level 2    
Assets:    
Commodity derivative assets – current   97,956,000
Liabilities:    
Derivative liabilities, current (12,932,000)  
Derivative liabilities, noncurrent (14,437,000)  
Fair Value, Measurements, Recurring | Commodity contracts | Level 3    
Assets:    
Commodity derivative assets – current   $ 0
Liabilities:    
Derivative liabilities, current 0  
Derivative liabilities, noncurrent $ 0