Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Prepaid Expenses and Other Current Assets
Rio Grande LNG site option	$ 365	$ 508
Short-term security deposits	27	18
Rio Bravo Pipeline options	40	54
Prepaid insurance	191	233
Prepaid marketing and sponsorships	782	242
Other	376	255
Total prepaid expenses and other current assets	$ 1,781	$ 1,310