Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member] Class A Common Stock [Member]	Common Stock [Member] Class B Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning balance at Dec. 31, 2018	$ 293,686	$ 4	$ 3	$ 379,832	$ (74,863)	$ (11,290)
Beginning balance (in shares) at Dec. 31, 2018		38,349	32,171
Net income	13,019				13,019
Exercise of stock options	458			458
Exercise of stock options (in shares)		397
Vesting of restricted stock (in shares)		14
Stock-based compensation	869			869
Foreign currency translation, net of tax	337					337
Retirement related benefit plans, net of tax	228					228
Ending balance at Mar. 31, 2019	308,597	$ 4	$ 3	381,159	(61,844)	(10,725)
Ending balance (in shares) at Mar. 31, 2019		38,760	32,171
Beginning balance at Dec. 31, 2019	354,707	$ 4	$ 3	446,633	(82,405)	(9,528)
Beginning balance (in shares) at Dec. 31, 2019		41,271	31,131
Cumulative effect of an accounting change at Dec. 31, 2019	(388)				(388)
Net income	6,030				6,030
Exercise of stock options	194			194
Exercise of stock options (in shares)		285
Vesting of restricted stock (in shares)		143
Conversion from Class B to Class A common stock		80	(80)
Stock-based compensation	3,043			3,043
Foreign currency translation, net of tax	(7,578)					(7,578)
Retirement related benefit plans, net of tax	137					137
Ending balance at Mar. 31, 2020	$ 356,145	$ 4	$ 3	$ 449,870	$ (76,763)	$ (16,969)
Ending balance (in shares) at Mar. 31, 2020		41,779	31,051