Variable Interest Entities - VIE Financials (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
ASSETS
Cash and cash equivalents	$ 42,207		$ 42,207			$ 85,249
Restricted cash	25,516		25,516			38,911
Investment in alternative assets, fair value	226,138		226,138			221,894
Other assets	33,256		33,256			36,326
TOTAL ASSETS	3,490,196		3,490,196			3,564,957
LIABILITIES
Accounts payable and accrued expenses	30,448		30,448			26,505
TOTAL LIABILITIES	2,063,192		2,063,192			1,891,050
Equity (Deficit):
Noncontrolling interests	316,687		316,687			328,442
Total Equity of VIE	200,984	$ 494,656	200,984	$ 494,656	$ 267,731	440,814	$ 499,196	$ 607,194
REVENUE
Investment income, net	17,554	56,705	21,417	41,590
Interest income	213	278	835	1,293
Revenue	33,786	68,012	37,259	119,742
EXPENSES
Other expenses	9,652	4,712	23,050	13,387
TOTAL EXPENSES	76,269	87,111	216,464	272,149
Net loss			(191,276)	(142,141)
Net (income) loss attributable to noncontrolling interests	(87)	(21,181)	29,766	32,901
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON SHAREHOLDERS	(50,578)	(48,898)	(169,881)	(120,475)
Variable Interest Entity, Primary Beneficiary | ExAlt Trusts
ASSETS
Cash and cash equivalents	2,240		2,240			5,965
Restricted cash	4,469		4,469			5,386
Investment in alternative assets, fair value	226,138		226,138			221,894
Other assets	1,278		1,278			1,273
TOTAL ASSETS	234,125		234,125			234,518
LIABILITIES
Accounts payable and accrued expenses	2,065		2,065			2,029
TOTAL LIABILITIES	2,065		2,065			2,029
Equity (Deficit):
Noncontrolling interests	(14,469)		(14,469)			7,208
Total Equity of VIE	(14,469)		(14,469)			$ 7,208
REVENUE
Investment income, net	17,554	56,705	21,417	41,590
Interest income	0	0	0	20
Revenue	17,554	56,705	21,417	41,610
EXPENSES
Other expenses	215	162	572	330
TOTAL EXPENSES	215	162	572	330
Net loss	17,339	56,543	20,845	41,280
Net (income) loss attributable to noncontrolling interests	(2,936)	(33,926)	(20,931)	9,795
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 14,403	$ 22,617	$ (86)	$ 51,075