Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Accrued Expenses and Other Current Liabilities
Accrued salaries and benefits	$ 1,259	$ 1,332
Accrued severance and other charges	1,647	1,092
Accrued warranty	244	228	$ 342	$ 373
Warrant liability	360	3,072
Liability for consigned precious metals	1,052	543
Other	1,710	1,587
Accrued expenses and other current liabilities	$ 6,272	$ 7,854