Sale of Oil and Natural Gas Property Interest - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of assets	$ (290)	$ 5,183	$ 1,585
Assets held for sale	3,162	$ 3,162		$ 20,673
Central Processing Facility and Certain Pipelines[Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale proceeds of assets	37,300
Gain on sale of assets	$ 5,200