Other Income - Other Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Other Income And Expenses [Abstract]
Gains and losses from sale, disposal and retirement of property, equipment and easements, net	$ 42	$ 498
Interest and other	33	8
Other income, net	$ 75	$ 506