Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Payables and Accruals [Abstract]
Payroll and other employee related costs	$ 12,556	$ 16,431
Professional services and consulting and other vendor fees	14,287	15,674
Unrecognized tax benefits	2,348	4,924
Sales commissions	3,048	5,259
Restructuring	1,485	2,338	$ 2,551
Other	4,487	3,385
Total	$ 38,211	$ 48,011