Segment Information - Geographic region (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Information
Total revenue	$ 14,946	$ 13,194	$ 12,914	$ 14,257	$ 18,730	$ 18,257	$ 15,008	$ 19,862	$ 55,311	$ 71,857	$ 73,414
United States
Segment Information
Total revenue									55,273	70,319	54,760
Europe
Segment Information
Total revenue									$ 38	$ 1,538	$ 18,654