Restructuring Activities - Charges and Net Assets (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Total Revenues	$ 4,401		$ 8,948		$ 8,179	$ 19,103
Net loss	(2,544)	$ (2,567)	(945)	$ (1,289)	(5,111)	(2,234)
Total assets	28,557				28,557		$ 32,224
Liabilities	7,427				7,427		6,049
Restructuring charge	0		30		0	625
CHINA
Restructuring Cost and Reserve [Line Items]
Remaining performance requirements for APC projects	29				29
Total Revenues	3		(28)		5	310
Net loss	(85)		(540)		42	(1,390)
Total assets	3,072				3,072		4,249
Liabilities	352				352		399
Total net assets	$ 2,720				$ 2,720		$ 3,850
CHINA | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charge			$ 30
CHINA | Facility Closing
Restructuring Cost and Reserve [Line Items]
Restructuring charge						$ 625