Property and Equipment Long-lived assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment, net	$ 52,039	$ 51,500
United States
Property, Plant and Equipment [Line Items]
Total property and equipment, net	45,656	44,684
Rest of world
Property, Plant and Equipment [Line Items]
Total property and equipment, net	$ 6,383	$ 6,816