Summary of Significant Accounting Policies - Summary for Concentration of Receivables, Net of Allowances, By Product or Service (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Revenue, Major Customer [Line Items]
Concentration of receivables, net of allowances	$ 25,638	$ 27,476
Product Concentration Risk [Member] | Oil and Natural Gas and Related Products and Services [Member]
Revenue, Major Customer [Line Items]
Concentration of receivables, net of allowances	18,110	19,858
Product Concentration Risk [Member] | Joint Interest Owners [Member]
Revenue, Major Customer [Line Items]
Concentration of receivables, net of allowances	6,085	3,095
Product Concentration Risk [Member] | Derivatives [Member]
Revenue, Major Customer [Line Items]
Concentration of receivables, net of allowances	1,424	$ 4,523
Product Concentration Risk [Member] | Miscellaneous Other [Member]
Revenue, Major Customer [Line Items]
Concentration of receivables, net of allowances	$ 19