Liabilities - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accrued expenses and other current liabilities
Payroll and related benefits	$ 30,890	$ 32,996
Warranty	6,455	6,532
Interest	2,148	4,430
Professional fees	3,654	3,942
Merger consideration payable	2,662	2,662
Sales, use, and other taxes	1,493	2,144
Restructuring liability	1,390	1,520
Other	5,605	3,842
Total	$ 54,297	$ 58,068