Income Taxes - Components of Net Deferred Income Tax Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred income tax assets:
Net operating loss carryforward	$ 9	$ 56
Asset retirement obligation	875	694
Other	33	38
Total deferred income tax assets:	917	788
Valuation allowance	(865)	0
Net deferred income tax assets	52	788
Deferred income tax liabilities:
Property, plant and equipment	1,522	1,324
Derivatives	770	1,514
Other	40	44
Total deferred income tax liabilities	2,332	2,882
Net deferred income tax liabilities	$ 2,280	$ 2,094