Stockholders' Equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	$ 160,206	$ 160,240	$ 194,451	$ 225,405
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(7,641)	(6,897)
Unrealized loss on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	0	0
Defined benefit pension plan adjustment, net of taxes
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	230	229
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	$ (7,871)	$ (7,126)	$ 398	$ (8,401)