Geographic Information - Schedule of Long-Lived Assets by Geographic Areas (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	$ 41,369	$ 47,266
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	23,609	26,372
EMEA
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	10,026	12,537
Republic of Ireland
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	5,019	5,703
Other EMEA
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	5,007	6,834
APAC
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	$ 7,734	$ 8,357