Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Prepaid Expenses and Other Current Assets
Prepaid expenses and other current assets	$ 2,240	$ 2,790
Prepaid rent	19	165
Leasehold improvement incentives	55	766
Deferred rental income	91
Total prepaid expenses and other current assets	$ 2,405	$ 3,721