Business Segment, Geographic and Major Customer Information - Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 79,458	$ 64,337	$ 244,589	$ 192,227
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	66,638	52,545	203,123	154,532
Other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 12,820	$ 11,792	$ 41,466	$ 37,695