Segment Reporting (Details) $ in Thousands	3 Months Ended		9 Months Ended				12 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment		Sep. 30, 2020 USD ($)		Dec. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			2
Reconciliation to U.S. GAAP Company's Economic Income (Loss)
Preferred stock dividends	$ 1,698	$ 1,698	$ 5,094		$ 5,094
Amortization of (discount)/premium on convertible debt			6,695		3,393
Bargain Purchase Gain, net of tax	0	0	3,855		0
Goodwill Impairment			0				$ 0
Income tax expense (benefit)	12,192	8,830	76,864		52,589
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	32,865	29,516	244,009		104,353
Segment Information
Total revenues	412,237	321,296	1,618,519		1,164,203
Depreciation and Amortization	4,796	5,682	13,715		17,324
Income tax expense (benefit)	12,192	8,830	76,864		52,589
Interest and Dividend Expense	43,035	37,754	163,749		125,850
Dividend expense	2,500	700	6,100		5,800
Dividend revenue	5,800	2,100	17,900		12,600
Consolidated Funds
Segment Information
Interest and Dividend Expense	0	0	0		2,064
Dividend expense		0			400
Dividend revenue			0		2,400
Operating Segments
Segment Information
Non-Interest Revenue	372,033	284,756	1,468,891	[1]	1,047,688	[1]
Interest Revenue	40,202	35,405	149,621		114,954
Total revenues	412,237	321,296	1,618,519		1,164,203
Operating Segments | Consolidated Funds
Segment Information
Interest Revenue	2	1,135	7		1,561
Adjustments
Reconciliation to U.S. GAAP Company's Economic Income (Loss)
Noncontrolling Interest (Adjusted)	(4,938)	9,232	13,379		(19,843)
Preferred stock dividends	1,698	1,698	5,094		5,094
Amortization of (discount)/premium on convertible debt	(26)	(1,152)	(1,571)		(3,394)
Acquisition related amounts	(1,007)	(171)	(1,324)		(34)
Contingent Consideration Payable	(4,244)	(3,023)	(2,677)		(4,781)
Debt extinguishment gain (loss) and accelerated debt costs	0	0	(10,095)		0
Bargain Purchase Gain, net of tax	0	0	3,855		0
Goodwill Impairment	0	0	0		(545)
Income tax expense (benefit)	1,663	(8,830)	7,752		(52,589)
Segment Information
Income tax expense (benefit)	1,663	(8,830)	7,752		(52,589)
OpCo | Operating Segments
Reconciliation to U.S. GAAP Company's Economic Income (Loss)
Economic Income	43,496	32,790	238,500		200,774
Income tax expense (benefit)	13,484	8,830	80,333		52,589
Segment Information
Non-Interest Revenue	373,695	276,496	1,469,034		1,042,986
Interest Revenue	40,025	35,257	149,033		114,560
Total revenues	413,720	312,885	1,618,067		1,159,100
Interest Expense	39,592	35,701	153,542		115,314
Depreciation and Amortization	4,791	5,677	13,701		17,307
Income tax expense (benefit)	13,484	8,830	80,333		52,589
OpCo | Operating Segments | Consolidated Funds
Segment Information
Interest Revenue	0	1,132	0		1,554
Interest Expense	0	0	0		1,672
Asset Co | Operating Segments
Reconciliation to U.S. GAAP Company's Economic Income (Loss)
Economic Income	(3,777)	(1,028)	(8,904)		(20,329)
Income tax expense (benefit)	(1,292)	0	(3,469)		0
Segment Information
Non-Interest Revenue	(1,662)	8,260	(143)		4,702
Interest Revenue	177	148	588		394
Total revenues	(1,483)	8,411	452		5,103
Interest Expense	901	1,357	4,106		4,772
Depreciation and Amortization	5	5	14		17
Income tax expense (benefit)	(1,292)	0	(3,469)		0
Asset Co | Operating Segments | Consolidated Funds
Segment Information
Interest Revenue	2	3	7		7
Interest Expense	$ 0	$ 0	$ 0		$ 0

[1] Includes dividend revenue of $5.8 million and $2.1 million for the three months ended September 30, 2021 and 2020, respectively and $17.9 million and $12.6 million for the nine months ended September 30, 2021 and 2020, respectively. In addition, includes dividend revenue, consolidated funds, of $0.0 million and $2.4 million for the three and nine months ended September 30, 2020, respectively.