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Supplemental Crude Oil and Natural Gas Information - Additional Information (Detail)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2017
MBoe
Dec. 31, 2017
MMcf
Dec. 31, 2017
MBbls
Dec. 31, 2017
$ / Barrels
Dec. 31, 2016
$ / bbl
$ / Mcf
MBoe
MMcf
MBbls
Dec. 31, 2015
$ / bbl
$ / Mcf
MBoe
MMcf
MBbls
Reserve Quantities [Line Items]              
Extensions, discoveries, and other additions   240,206       249,430 253,173
Discount factor utilized as standardized measure for future net cash flows 10.00%            
Crude Oil [Member]              
Reserve Quantities [Line Items]              
Weighted average price utilized in computation of future cash inflows         47.03 35.57 41.63
Crude Oil [Member]              
Reserve Quantities [Line Items]              
Percentage change in average SEC price 20.00%            
Revisions of previous estimates | MBbls       (77,779)   (99,966) (246,840)
Extensions, discoveries and other additions | MBbls       129,895   97,587 134,764
Natural Gas [Member]              
Reserve Quantities [Line Items]              
Percentage change in average SEC price 20.00%            
Revisions of previous estimates | MMcf     (25,390)     (63,057) (302,143)
Extensions, discoveries and other additions | MMcf     661,867     911,062 710,453
Weighted average price utilized in computation of future cash inflows         3.00 2.14 2.35
Proved Undeveloped Reserves [Domain]              
Reserve Quantities [Line Items]              
Revisions of previous estimates   89          
Proved Undeveloped Reserves [Domain] | Natural Gas [Member]              
Reserve Quantities [Line Items]              
Revisions of previous estimates | MMcf     290        
Proved Undeveloped Reserves [Domain] | Crude Oil [Member]              
Reserve Quantities [Line Items]              
Revisions of previous estimates | MBbls       41      
Bakken [Member]              
Reserve Quantities [Line Items]              
Extensions, discoveries and other additions     253,000 106,000      
Extensions, discoveries, and other additions   148,000          
SCOOP [Member]              
Reserve Quantities [Line Items]              
Revisions of previous estimates   53,000          
Extensions, discoveries and other additions     224,000 16,000      
STACK [Member]              
Reserve Quantities [Line Items]              
Revisions of previous estimates   39,000          
Extensions, discoveries and other additions     185,000 8,000      
Production Type [Domain] | Proved Reserves [Domain]              
Reserve Quantities [Line Items]              
Revisions of previous estimates   30          
Production Type [Domain] | Proved Reserves [Domain] | Natural Gas [Member]              
Reserve Quantities [Line Items]              
Revisions of previous estimates | MMcf     173        
Production Type [Domain] | Proved Reserves [Domain] | Crude Oil [Member]              
Reserve Quantities [Line Items]              
Revisions of previous estimates | MBbls       59      
Price Driven [Domain] | Proved Reserves [Domain]              
Reserve Quantities [Line Items]              
Revisions of previous estimates   42          
Price Driven [Domain] | Proved Reserves [Domain] | Natural Gas [Member]              
Reserve Quantities [Line Items]              
Revisions of previous estimates | MMcf     78        
Price Driven [Domain] | Proved Reserves [Domain] | Crude Oil [Member]              
Reserve Quantities [Line Items]              
Revisions of previous estimates | MBbls       29