Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Accrued Expenses and Other Current Liabilities
Accrued salaries and benefits	$ 654	$ 759
Accrued severance and other charges	1,348	1,738
Accrued warranty	325	338	$ 242	$ 228
Warrant liability	1,564	1,226
Liability for consigned precious metals	1,472	1,282
Other	1,013	1,002
Accrued expenses and other current liabilities	$ 6,376	$ 6,345