Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Preferred Stock	Additional Paid-in Capital	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Total Attributed To Shareholders	Non- controlling Interests
Balance (in shares) at Dec. 31, 2018		6,997,382	1,150,000				3,555,242
Beginning Balance at Dec. 31, 2018	$ 643,867	$ 106	$ 110,843	$ 1,209,805	$ (310,865)	$ (731)	$ (379,249)	$ 629,909	$ 13,958
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	94,622				95,649			95,649	(1,027)
Foreign currency translation adjustment	14					14		14
Net subscriptions (redemptions) and other	(1,535)			838				838	(2,373)
Reclassification from other comprehensive (income) loss	726					726		726
Cash dividends declared. preferred	(8,337)			(8,337)				(8,337)
Cash dividends declared, common	(18,130)			(18,130)				(18,130)
Repurchase of common shares (in shares)		(372,365)					372,365
Repurchase of common shares	(40,000)						$ (40,000)	(40,000)
Issuance of common shares related to employee stock transactions (in shares)		184,263
Issuance of common shares related to employee stock transactions	1,553	$ 1		1,552				1,553
Taxes paid on stock-based compensation	(7,696)			(7,696)				(7,696)
Stock-based compensation	21,173			21,173				21,173
Balance (in shares) at Dec. 31, 2019		6,809,280	1,150,000				3,927,607
Ending Balance at Dec. 31, 2019	686,257	$ 107	$ 110,843	1,199,205	(215,216)	9	$ (419,249)	675,699	10,558
Balance at Dec. 31, 2018	57,481
Increase (Decrease) in Redeemable Non-controlling Interests [Roll Forward]
Net income (loss)	10,886
Net subscriptions (redemptions) and other	(4,522)
Balance at Dec. 31, 2019	63,845
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	81,255				79,957			79,957	1,298
Foreign currency translation adjustment	20					20		20
Net subscriptions (redemptions) and other	(2,224)			(167)				(167)	(2,057)
Cash dividends declared, common	(24,998)			(24,998)				(24,998)
Conversion of preferred stock (in shares)		912,806	(1,150,000)
Conversion of preferred stock	0	$ 9	$ (110,843)	110,834				0
Repurchase of common shares (in shares)		(279,796)					279,796
Repurchase of common shares	(32,500)						$ (32,500)	(32,500)
Issuance of common shares related to employee stock transactions (in shares)		141,176
Issuance of common shares related to employee stock transactions	186	$ 2		184				186
Taxes paid on stock-based compensation	(6,608)			(6,608)				(6,608)
Stock-based compensation	19,552			19,552				19,552
Balance (in shares) at Dec. 31, 2020		7,583,466	0				4,207,403
Ending Balance at Dec. 31, 2020	720,940	$ 118	$ 0	1,298,002	(135,259)	29	$ (451,749)	711,141	9,799
Increase (Decrease) in Redeemable Non-controlling Interests [Roll Forward]
Net income (loss)	38,708
Net subscriptions (redemptions) and other	12,960
Balance at Dec. 31, 2020	115,513
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	208,948				208,131			208,131	817
Foreign currency translation adjustment	(9)					(9)		(9)
Net subscriptions (redemptions) and other	(2,266)			0				0	(2,266)
Cash dividends declared, common	(37,222)			(25,312)	(11,910)			(37,222)
Repurchase of common shares (in shares)		(193,193)					193,193
Repurchase of common shares	(57,499)						$ (57,499)	(57,499)
Issuance of common shares related to employee stock transactions (in shares)		115,878
Issuance of common shares related to employee stock transactions	66	$ 1		65				66
Taxes paid on stock-based compensation	(19,509)			(19,509)				(19,509)
Stock-based compensation	23,178			23,178				23,178
Balance (in shares) at Dec. 31, 2021		7,506,151	0				4,400,596
Ending Balance at Dec. 31, 2021	836,627	$ 119	$ 0	$ 1,276,424	$ 60,962	$ 20	$ (509,248)	$ 828,277	$ 8,350
Increase (Decrease) in Redeemable Non-controlling Interests [Roll Forward]
Net income (loss)	53,887
Net subscriptions (redemptions) and other	(30,435)
Balance at Dec. 31, 2021	$ 138,965