Business Segment, Geographic and Major Customer Information - Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 21,879	$ 53,709	$ 99,827	$ 134,324
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	19,663	35,685	89,653	108,571
Other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 2,216	$ 18,024	$ 10,174	$ 25,753