Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Prepaid Expenses and Other Current Assets
Rio Grande LNG site option	$ 635	$ 1,080
Short-term security deposits	367	364
Galveston Bay leases	125	100
Rio Bravo Pipeline options	68	111
Prepaid insurance	289	208
Prepaid marketing and sponsorships	91	55
Other	229	181
Total prepaid expenses and other current assets	$ 1,804	$ 2,099