Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Accrued Expenses and Other Current Liabilities
Accrued salaries and benefits	$ 1,284	$ 1,332
Accrued severance and other charges	1,565	1,092
Accrued warranty	242	228	$ 343	$ 373
Warrant liability	1,537	3,072
Liability for consigned precious metals	1,038	543
Other	1,595	1,587
Accrued expenses and other current liabilities	$ 7,261	$ 7,854