Series B Convertible Preferred Stock and Stockholders’ Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
TOTAL STOCKHOLDERS' EQUITY	$ 272,393	$ 270,962	$ 304,895	$ 320,324	$ 333,686	$ 333,316	$ 333,229	$ 347,701	$ 364,313	$ 407,637
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
TOTAL STOCKHOLDERS' EQUITY	(31,667)				(31,060)				$ (28,837)	$ (12,769)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
TOTAL STOCKHOLDERS' EQUITY	(31,368)				(32,880)
Unrealized gain on hedging activity
Accumulated Other Comprehensive Income (Loss) [Line Items]
TOTAL STOCKHOLDERS' EQUITY	0				1,876
Pension and other postretirement benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
TOTAL STOCKHOLDERS' EQUITY	$ (299)				$ (56)