Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued Expenses and Other Current Liabilities
Payroll and related costs	$ 9,607	$ 6,923
Employee benefits	5,281	4,701
Accrued warranty	3,662	3,262
Other	4,756	6,118
Accrued expenses and other current liabilities	$ 23,306	$ 21,004