Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Prepaid Expenses and Other Current Assets
Rio Grande LNG site option	$ 1,080	$ 495
Short-term security deposits	364	349
Galveston Bay Leases	100
Rio Bravo Pipeline options	111	86
Prepaid insurance	208	21
Other	236	145
Total prepaid expenses and other current assets	2,099	1,096
Lease option expense relating to Rio Grande LNG site option	$ 584	$ 584	$ 584