Realized and Net Change in Unrealized Gains (Losses) on Financial Instruments on Financial Instruments on Which Fair Value Option was Elected (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Debt Securities \| Realized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments	$ 0	$ 0	$ (11,226)	$ 642
Debt Securities \| Net Change in Unrealized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments	(236)	(2,808)	8,319	(3,822)
Assets \| Realized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments	892	30	(9,039)	(9,760)
Assets \| Net Change in Unrealized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments	85,041	(9,975)	115,405	15,137
Loans and Receivables \| Realized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments	592	(273)	560	(929)
Loans and Receivables \| Net Change in Unrealized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments	(1,813)	245	(2,966)	221
Liabilities \| Net Change in Unrealized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments	439	512	(1,418)	935
Equity and Preferred Securities \| Realized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments	300	303	1,627	(7,761)
Equity and Preferred Securities \| Net Change in Unrealized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments	87,090	(7,412)	110,052	17,700
Corporate Loans \| Realized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments				(1,712)
Corporate Loans \| Net Change in Unrealized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments				1,038
CLO Notes Payable \| Net Change in Unrealized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments				859
Corporate Treasury Commitments \| Net Change in Unrealized Gains (Losses)
Fair Value, Option, Quantitative Disclosures [Line Items]
Realized and net change in unrealized gains (losses) on financial instruments	$ 439	$ 512	$ (1,418)	$ 76