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, 2018	$ 332,732				$ 6	$ 2	$ 1		$ 862,299	$ (528,164)	$ (1,412)
Balance, Beginning, Shares at Dec. 31, 2018					63,210,531	14,927,613	9,352,729
Issuance of common stock upon exercise of stock options or awards of restricted stock units, Shares	49,000
Tax payments related to shares withheld for share-based compensation plans	$ (979)								(979)
Tax payments related to shares withheld for share-based compensation plans, shares					673,732
Stock-based compensation expense	4,377								4,377
Repurchase of Class A common stock	(12,565)	$ (12,600)							(12,565)
Repurchase of Class A common stock, Shares		(3,800,000)			(3,809,565)			3,809,565
Retirement of treasury stock, Shares								(3,809,565)
Dividends paid	(16,962)								16,962
Change in fair value of marketable securities	1,428										1,428
Foreign currency translation gain (loss)	(147)										(147)
Net income (loss) attributable to common stockholders	(19,712)									(19,712)
Balance, Ending at Dec. 31, 2019	$ 288,172				$ 6	$ 2	$ 1		836,170	(547,876)	(131)
Balance, Ending, Shares at Dec. 31, 2019					60,074,698	14,927,613	9,352,729
Issuance of common stock upon exercise of stock options or awards of restricted stock units, Shares	10,000
Tax payments related to shares withheld for share-based compensation plans	$ (1,426)								(1,426)
Tax payments related to shares withheld for share-based compensation plans, shares					944,207
Stock-based compensation expense	5,125								5,125
Repurchase of Class A common stock	(525)	$ (500)							(525)
Repurchase of Class A common stock, Shares		(300,000)			(259,500)			259,500
Retirement of treasury stock, Shares								(259,500)
Dividends paid	(10,531)								(10,531)
Change in fair value of marketable securities	(3)										(3)
Foreign currency translation gain (loss)	(922)										(922)
Net income (loss) attributable to common stockholders	(3,910)									(3,910)
Balance, Ending at Dec. 31, 2020	275,980				$ 6	$ 2	$ 1		828,813	(551,786)	(1,056)
Balance, Ending, Shares at Dec. 31, 2020		60,759,405	14,927,613	9,352,729	60,759,405	14,927,613	9,352,729
Issuance of common stock upon exercise of stock options or awards of restricted stock units	$ 416								416
Issuance of common stock upon exercise of stock options or awards of restricted stock units, Shares	533,000				151,000
Tax payments related to shares withheld for share-based compensation plans	$ (4,729)								(4,729)
Tax payments related to shares withheld for share-based compensation plans, shares					1,406,491
Stock-based compensation expense	9,595								9,595
Class B common stock exchanged for Class A common stock, shares					800,000	(800,000)
Repurchase of Class A common stock	(32,200)
Repurchase of Class A common stock, Shares		(8,600,000)
Dividends paid	(8,531)								(8,531)
Change in fair value of marketable securities	(105)										(105)
Foreign currency translation gain (loss)	184										184
Acquisition of redeemable noncontrolling interest	(45,176)								(45,176)
Net income (loss) attributable to common stockholders	29,292									29,292
Balance, Ending at Dec. 31, 2021	$ 256,926				$ 6	$ 2	$ 1		$ 780,388	$ (522,494)	$ (977)
Balance, Ending, Shares at Dec. 31, 2021		63,116,896	14,127,613	9,352,729	63,116,896	14,127,613	9,352,729