Summary of Accounts Receivable (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Receivables [Abstract]
Customers	$ 59,906	$ 62,650
Joint interest partners	39,412	120,708
Other	5,873	6,549
Accounts Receivable, Gross, Current, Total	105,191	189,907
Less: Allowance for doubtful accounts	(555)	(280)
Accounts receivable, net of allowance for doubtful accounts	$ 104,636	$ 189,627