Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Prepaid Expenses and Other Current Assets
Rio Grande LNG site option	$ 921	$ 1,080
Short-term security deposits	367	364
Galveston Bay leases	125	100
Rio Bravo Pipeline options	97	111
Prepaid insurance	167	208
Prepaid marketing sponsorships	353	55
Other	252	181
Total prepaid expenses and other current assets	$ 2,282	$ 2,099