Business Segment and Geographic Financial Data - Operations by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues:
Revenues	$ 4,401	$ 8,948	$ 8,179	$ 19,103
United States
Revenues:
Revenues	3,310	7,562	6,407	16,377
Foreign
Revenues:
Revenues	$ 1,091	$ 1,386	$ 1,772	$ 2,726