Summary of Accounts Receivable (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Receivables [Abstract]
Customers	$ 37,010	$ 62,650
Joint interest partners	29,693	120,708
Other	7,872	6,549
Accounts Receivable, Gross, Current, Total	74,575	189,907
Less: Allowance for doubtful accounts	(1,555)	(280)
Accounts receivable, net of allowance for doubtful accounts	$ 73,020	$ 189,627