Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Series D convertible preferred stock	Common Stock	Preferred Stock	Preferred Stock Series D convertible preferred stock	Additional Paid-in Capital	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Total Attributed To Stockholders	Non- controlling Interests
Beginning 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)	21,293						21,746			21,746	(453)
Foreign currency translation adjustments	6							6		6
Net subscriptions (redemptions) and other	(557)										(557)
Reclassification from other comprehensive (income) loss		$ 726						726		726
Cash dividends declared, preferred	(2,084)					(2,084)				(2,084)
Cash dividends declared, common	(4,152)					(4,152)				(4,152)
Repurchases of common shares (in shares)			(147,962)						(147,962)
Repurchases of common shares	(14,999)								$ (14,999)	(14,999)
Issuance of common shares related to employee stock transactions (in shares)			129,505
Issuance of common shares related to employee stock transactions	449		$ 1			448				449
Taxes paid on stock-based compensation	(4,804)					(4,804)				(4,804)
Stock-based compensation	6,713					6,713				6,713
Ending Balance (in shares) at Mar. 31, 2019			6,978,925		1,150,000				3,703,204
Ending Balance at Mar. 31, 2019	646,458		$ 107		$ 110,843	1,205,926	(289,119)	1	$ (394,248)	633,510	12,948
Beginning Balance at Dec. 31, 2018	57,481
Increase (Decrease) in Redeemable Non-controlling Interests [Roll Forward]
Total net income (loss) attributable to noncontrolling interests	1,175
Net subscriptions (redemptions) and other	347
Ending Balance at Mar. 31, 2019	59,003
Beginning 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
Ending 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
Beginning Balance at Dec. 31, 2018	57,481
Increase (Decrease) in Redeemable Non-controlling Interests [Roll Forward]
Total net income (loss) attributable to noncontrolling interests	5,036
Ending Balance at Dec. 31, 2019	63,845
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(4,030)						(4,285)			(4,285)	255
Foreign currency translation adjustments	(25)							(25)		(25)
Net subscriptions (redemptions) and other	(566)									0	(566)
Cash dividends declared, common	$ (6,180)					(6,180)				(6,180)
Repurchases of common shares (in shares)	(110,956)		(110,956)						(110,956)
Repurchases of common shares	$ (10,000)								$ (10,000)	(10,000)
Conversion of preferred stock (in shares)			912,806	(1,150,000)
Conversion of preferred stock	0		$ 9	$ (110,843)		110,834				0
Issuance of common shares related to employee stock transactions (in shares)			84,283
Issuance of common shares related to employee stock transactions	101		$ 1			100				101
Taxes paid on stock-based compensation	(3,550)					(3,550)				(3,550)
Stock-based compensation	4,459					4,459				4,459
Ending Balance (in shares) at Mar. 31, 2020			7,695,413		0				4,038,563
Ending Balance at Mar. 31, 2020	666,466		$ 117		$ 0	$ 1,304,868	$ (219,501)	$ (16)	$ (429,249)	$ 656,219	$ 10,247
Increase (Decrease) in Redeemable Non-controlling Interests [Roll Forward]
Total net income (loss) attributable to noncontrolling interests	5,036
Net subscriptions (redemptions) and other	18,234
Ending Balance at Mar. 31, 2020	$ 87,115