Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	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 Deficit [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning balance at Dec. 31, 2019	$ 354,707	$ (388)	$ 4	$ 3	$ 446,633	$ (82,405)	$ (388)	$ (9,528)
Beginning balance (in shares) at Dec. 31, 2019			41,271	31,131
Net income (loss)	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
Beginning balance at Dec. 31, 2019	354,707	$ (388)	$ 4	$ 3	446,633	(82,405)	$ (388)	(9,528)
Beginning balance (in shares) at Dec. 31, 2019			41,271	31,131
Net income (loss)	(12,698)
Foreign currency translation, net of tax	(446)
Retirement related benefit plans, net of tax	110
Ending balance at Sep. 30, 2020	359,455		$ 4	$ 3	464,803	(95,491)		(9,864)
Ending balance (in shares) at Sep. 30, 2020			42,870	30,591
Beginning balance at Mar. 31, 2020	356,145		$ 4	$ 3	449,870	(76,763)		(16,969)
Beginning balance (in shares) at Mar. 31, 2020			41,779	31,051
Net income (loss)	(10,223)					(10,223)
Exercise of stock options	283				283
Exercise of stock options (in shares)			197
Vesting of restricted stock (in shares)			52
Conversion from Class B to Class A common stock			80	(80)
Stock-based compensation	4,586				4,586
Reclassification of mezzanine equity to permanent equity	1,568				1,568
Foreign currency translation, net of tax	2,560							2,560
Retirement related benefit plans, net of tax	31							31
Ending balance at Jun. 30, 2020	354,950		$ 4	$ 3	456,307	(86,986)		(14,378)
Ending balance (in shares) at Jun. 30, 2020			42,108	30,971
Net income (loss)	(8,505)					(8,505)
Issuance of common stock for acquisitions	1,638				1,638
Issuance of common stock for acquisitions (in shares)			40
Exercise of stock options	618				618
Exercise of stock options (in shares)			328
Vesting of restricted stock (in shares)			14
Conversion from Class B to Class A common stock			380	(380)
Stock-based compensation	6,240				6,240
Foreign currency translation, net of tax	4,572							4,572
Retirement related benefit plans, net of tax	(58)							(58)
Ending balance at Sep. 30, 2020	359,455		$ 4	$ 3	464,803	(95,491)		(9,864)
Ending balance (in shares) at Sep. 30, 2020			42,870	30,591
Beginning balance at Dec. 31, 2020	378,586		$ 4	$ 3	474,669	(93,293)		(2,797)
Beginning balance (in shares) at Dec. 31, 2020			44,216	30,111
Net income (loss)	14,360					14,360
Exercise of stock options	271				271
Exercise of stock options (in shares)			490
Vesting of restricted stock (in shares)			278
Conversion from Class B to Class A common stock			510	(510)
Stock-based compensation	9,644				9,644
Foreign currency translation, net of tax	(3,975)							(3,975)
Retirement related benefit plans, net of tax	143							143
Ending balance at Mar. 31, 2021	399,029		$ 4	$ 3	484,584	(78,933)		(6,629)
Ending balance (in shares) at Mar. 31, 2021			45,494	29,601
Beginning balance at Dec. 31, 2020	378,586		$ 4	$ 3	474,669	(93,293)		(2,797)
Beginning balance (in shares) at Dec. 31, 2020			44,216	30,111
Net income (loss)	(7,397)
Foreign currency translation, net of tax	(5,685)
Retirement related benefit plans, net of tax	344
Ending balance at Sep. 30, 2021	602,262		$ 5	$ 3	711,082	(100,690)		(8,138)
Ending balance (in shares) at Sep. 30, 2021			50,558	28,206
Beginning balance at Mar. 31, 2021	399,029		$ 4	$ 3	484,584	(78,933)		(6,629)
Beginning balance (in shares) at Mar. 31, 2021			45,494	29,601
Net income (loss)	(13,648)					(13,648)
Exercise of stock options	614				614
Exercise of stock options (in shares)			334
Vesting of restricted stock (in shares)			54
Conversion from Class B to Class A common stock			510	(510)
Stock-based compensation	10,626				10,626
Foreign currency translation, net of tax	2,640							2,640
Retirement related benefit plans, net of tax	84							84
Ending balance at Jun. 30, 2021	399,345		$ 4	$ 3	495,824	(92,581)		(3,905)
Ending balance (in shares) at Jun. 30, 2021			46,392	29,091
Net income (loss)	(8,109)					(8,109)
Issuance of common stock in private placement, net of issuance costs	199,872		$ 1		199,871
Issuance of common stock in private placement, net of issuance costs (in shares)			2,936
Issuance of common stock for acquisitions	3,280				3,280
Issuance of common stock for acquisitions (in shares)			53
Exercise of stock options	1,174				1,174
Exercise of stock options (in shares)			264
Vesting of restricted stock (in shares)			28
Conversion from Class B to Class A common stock			885	(885)
Stock-based compensation	10,933				10,933
Foreign currency translation, net of tax	(4,350)							(4,350)
Retirement related benefit plans, net of tax	117							117
Ending balance at Sep. 30, 2021	$ 602,262		$ 5	$ 3	$ 711,082	$ (100,690)		$ (8,138)
Ending balance (in shares) at Sep. 30, 2021			50,558	28,206