Portfolio Investments - NPRC Summarized Income Statement Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020
Investment Company, Nonconsolidated Subsidiary [Line Items]
Total income	$ 202,674	$ 184,623	$ 181,431	$ 175,376	$ 169,474	$ 157,339	$ 159,456	$ 172,292	$ 142,880
Operating expenses	103,408				88,105
Net Investment Income	99,266	$ 89,969	$ 87,005	$ 85,557	81,369	$ 73,229	$ 73,402	$ 81,561	$ 57,545
Interest expense	(33,870)				(28,038)
Fair value adjustment	(168,500)				136,720
Net (Decrease) Increase in Net Assets Resulting from Operations	(92,439)				212,131
NPRC
Investment Company, Nonconsolidated Subsidiary [Line Items]
Total income	103,621				94,370
Operating expenses	52,484				46,153
Net Investment Income	51,137				48,217
Interest expense	(69,479)				(51,732)
Depreciation and amortization	(29,323)				(29,165)
Fair value adjustment	(7,068)				2,132
Net (Decrease) Increase in Net Assets Resulting from Operations	$ (54,733)				$ (30,548)