Restructuring Activities - Charges and Net Assets (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Total revenues									$ 30,467	$ 56,535	$ 45,166
Net loss	$ (4,340)	$ (1,278)	$ (945)	$ (1,289)	$ 896	$ 1,045	$ (1,753)	$ (216)	(7,852)	(28)	(10,449)
Total assets	32,224				51,719				32,224	51,719
Total liabilities	6,049				17,667				6,049	17,667
CHINA
Restructuring Cost and Reserve [Line Items]
Total revenues									0	3	8
Net loss									(2)	(2)	(1)
Total assets	4				9				4	9	13
Total liabilities	0				3				0	3	5
Total net assets	$ 4				$ 6				$ 4	$ 6	$ 8