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Transactions with Controlled Companies - First Tower Finance Company LLC (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Jun. 30, 2022
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Interest Income	$ 190,876		$ 142,173	$ 365,194	$ 288,444
Structuring Fee	5,103		16,853	9,730	28,814
Total Other Income	19,823		27,499	45,278	49,435
Interest Receivable	33,709			33,709		$ 12,925
Other Receivables	974			$ 974		$ 745
First Tower Holdings of Delaware LLC \| First Tower Finance Company LLC
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Ownership interest		80.10%		80.10%		80.03%
First Tower Finance Company LLC \| First Tower, LLC
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Ownership interest				100.00%
Reportable Legal Entities \| Subsidiaries \| First Tower Holdings of Delaware LLC
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Ownership interest				100.00%
Reportable Legal Entities \| Subsidiaries \| First Tower Holdings of Delaware LLC
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Interest Income Capitalized as PIK	5,186		3,473	$ 14,762	7,250
Repayment of Loan Receivable	0		851	0	1,159
Interest Receivable	4,946			4,946		$ 218
Other Receivables	6			6		$ 6
Reportable Legal Entities \| Subsidiaries \| First Tower Finance Company LLC
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Interest Income	14,128		18,441	34,363	36,779
Structuring Fee	0		0	0	7,234
Total Other Income	0		0	0	7,234
Reportable Legal Entities \| Subsidiaries \| First Tower Finance Company LLC \| Prospect Administration
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Managerial Assistance	$ 1,200		$ 600	$ 1,200	$ 1,200