Investments - Schedule of Company's Investments in Limited Partnerships (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2022
Private US Lower Middle Market Companies [Member]
Schedule Of Investments [Line Items]
Expected term	10 years
Expected term	2 years
Bank Loans Public and Private Corporate Bonds Asset Backed Securities Equity and Debt Restructuring [Member]
Schedule Of Investments [Line Items]
Maturity date	Jun. 30, 2023
Investment additional maturity term	2 years
Power Utility and Energy Industries and Infrastructure [Member]
Schedule Of Investments [Line Items]
Expected term	10 years
Investment additional maturity term	3 years
Senior and Junior Debts of Private Equity-Backed Companies [Member]
Schedule Of Investments [Line Items]
Expected term	8 years
Investment additional maturity term	2 years
Mature Real Estate Private Equity Funds And Portfolio Globally [Member]
Schedule Of Investments [Line Items]
Maturity date	Nov. 27, 2027
Investment additional maturity term	4 years
Investment additional maturity term	2 years
Credit And Equity Investments Primarily In Private Equity Owned Companies [Member]
Schedule Of Investments [Line Items]
Expected term	8 years
Investment additional maturity term	1 year
Investment Additional Maturity Term With Consent Of Advisory Committee Or Majority	2 years