Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Class A common stock	Class B common stock	Class U common stock	Common Stock Class A common stock	Common Stock Class B common stock	Common Stock Class U common stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balance, Beginning at Dec. 31, 2020	$ 275,980				$ 6	$ 2	$ 1		$ 828,813	$ (551,786)	$ (1,056)
Balance, Beginning, Shares at Dec. 31, 2020					60,759,405	14,927,613	9,352,729
Issuance of common stock upon exercise of stock options or awards of restricted stock units	(9)								(9)
Issuance of common stock upon exercise of stock options or awards of restricted stock units, Shares					6,045
Stock-based compensation expense	1,071								1,071
Dividends paid	(2,126)								(2,126)
Change in fair value of marketable securities	(69)										(69)
Foreign currency translation gain (loss)	407										407
Net income (loss) attributable to common stockholders	5,429									5,429
Balance, Ending at Mar. 31, 2021	280,683				$ 6	$ 2	$ 1		827,749	(546,357)	(718)
Balance, Ending, Shares at Mar. 31, 2021					60,765,450	14,927,613	9,352,729
Balance, Beginning at Dec. 31, 2020	275,980				$ 6	$ 2	$ 1		828,813	(551,786)	(1,056)
Balance, Beginning, Shares at Dec. 31, 2020					60,759,405	14,927,613	9,352,729
Foreign currency translation gain (loss)	136
Net income (loss) attributable to common stockholders	13,293
Balance, Ending at Jun. 30, 2021	286,962				$ 6	$ 2	$ 1		826,474	(538,493)	(1,028)
Balance, Ending, Shares at Jun. 30, 2021					61,189,644	14,807,613	9,352,729
Balance, Beginning at Mar. 31, 2021	280,683				$ 6	$ 2	$ 1		827,749	(546,357)	(718)
Balance, Beginning, Shares at Mar. 31, 2021					60,765,450	14,927,613	9,352,729
Issuance of common stock upon exercise of stock options or awards of restricted stock units	(277)								(277)
Issuance of common stock upon exercise of stock options or awards of restricted stock units, Shares					304,194
Stock-based compensation expense	1,135								1,135
Class B common stock exchanged for Class A common stock, shares					120,000	(120,000)
Dividends paid	(2,133)								(2,133)
Change in fair value of marketable securities	(39)										(39)
Foreign currency translation gain (loss)	(271)										(271)
Net income (loss) attributable to common stockholders	7,864									7,864
Balance, Ending at Jun. 30, 2021	286,962				$ 6	$ 2	$ 1		826,474	(538,493)	(1,028)
Balance, Ending, Shares at Jun. 30, 2021					61,189,644	14,807,613	9,352,729
Balance, Beginning at Dec. 31, 2021	256,926				$ 6	$ 2	$ 1		780,388	(522,494)	(977)
Balance, Beginning, Shares at Dec. 31, 2021		63,116,896	14,127,613	9,352,729	63,116,896	14,127,613	9,352,729
Issuance of common stock upon exercise of stock options or awards of restricted stock units	218								218
Issuance of common stock upon exercise of stock options or awards of restricted stock units, Shares					66,000
Tax payments related to shares withheld for share-based compensation plans	(257)								(257)
Tax payments related to shares withheld for share-based compensation plans, shares					14,955
Stock-based compensation expense	2,573								2,573
Repurchase of Class A common stock	(7,142)								(7,142)
Repurchase of Class A common stock, shares					(1,114,470)			1,114,470
Retirement of treasury stock, shares								(1,114,470)
Dividends paid	(2,167)								(2,167)
Change in fair value of marketable securities	(283)										(283)
Net income (loss) attributable to common stockholders	1,887									1,887
Balance, Ending at Mar. 31, 2022	251,755				$ 6	$ 2	$ 1		773,613	(520,607)	(1,260)
Balance, Ending, Shares at Mar. 31, 2022					62,083,381	14,127,613	9,352,729
Balance, Beginning at Dec. 31, 2021	256,926				$ 6	$ 2	$ 1		780,388	(522,494)	(977)
Balance, Beginning, Shares at Dec. 31, 2021		63,116,896	14,127,613	9,352,729	63,116,896	14,127,613	9,352,729
Repurchase of Class A common stock		$ (11,300)
Repurchase of Class A common stock, shares		(1,800,000)
Foreign currency translation gain (loss)	(43)
Net income (loss) attributable to common stockholders	10,354
Balance, Ending at Jun. 30, 2022	255,293				$ 6	$ 2	$ 1		769,977	(512,140)	(2,553)
Balance, Ending, Shares at Jun. 30, 2022		61,465,531	14,127,613	9,352,729	61,465,531	14,127,613	9,352,729
Balance, Beginning at Mar. 31, 2022	251,755				$ 6	$ 2	$ 1		773,613	(520,607)	(1,260)
Balance, Beginning, Shares at Mar. 31, 2022					62,083,381	14,127,613	9,352,729
Tax payments related to shares withheld for share-based compensation plans	(10)								(10)
Tax payments related to shares withheld for share-based compensation plans, shares					20,681
Stock-based compensation expense	2,636								2,636
Repurchase of Class A common stock	(4,138)	$ (4,100)							(4,138)
Repurchase of Class A common stock, shares		(600,000)			(638,531)			(638,531)
Retirement of treasury stock, shares								(638,531)
Dividends paid	(2,124)								(2,124)
Change in fair value of marketable securities	(1,250)										(1,250)
Foreign currency translation gain (loss)	(43)										(43)
Net income (loss) attributable to common stockholders	8,467									8,467
Balance, Ending at Jun. 30, 2022	$ 255,293				$ 6	$ 2	$ 1		$ 769,977	$ (512,140)	$ (2,553)
Balance, Ending, Shares at Jun. 30, 2022		61,465,531	14,127,613	9,352,729	61,465,531	14,127,613	9,352,729