Investments - Schedule of Company's Investments in Limited Partnerships (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022
Investment Securities [Line Items]
Carrying Value		$ 23,583	$ 25,702
Unfunded Balance		4,205	5,661
Private US Lower Middle Market Companies [Member]
Investment Securities [Line Items]
Carrying Value	[1],[2],[3]	3,295	4,146
Unfunded Balance	[1],[2],[3]	$ 0	$ 0
Percentage investment held by the entity	[1],[2],[3],[4]	15.37%	15.37%
Bank Loans Public and Private Corporate Bonds Asset Backed Securities Equity and Debt Restructuring [Member]
Investment Securities [Line Items]
Carrying Value	[1],[2],[5]	$ 2,271	$ 2,528
Unfunded Balance	[1],[2],[5]	$ 0	$ 0
Percentage investment held by the entity	[1],[2],[4],[5]	1.25%	1.66%
Power Utility and Energy Industries and Infrastructure [Member]
Investment Securities [Line Items]
Carrying Value	[2],[6],[7]	$ 3,400	$ 5,319
Unfunded Balance	[2],[6],[7]	$ 0	$ 0
Percentage investment held by the entity	[2],[4],[6],[7]	0.18%	0.18%
Senior and Junior Debts of Private Equity-Backed Companies [Member]
Investment Securities [Line Items]
Carrying Value	[2],[8],[9]	$ 3,306	$ 3,470
Unfunded Balance	[2],[8],[9]	$ 0	$ 0
Percentage investment held by the entity	[2],[4],[8],[9]	0.55%	0.56%
Mature Real Estate Private Equity Funds And Portfolio Globally [Member]
Investment Securities [Line Items]
Carrying Value	[2],[10]	$ 7,590	$ 7,457
Unfunded Balance	[2],[10]	$ 2,543	$ 3,125
Percentage investment held by the entity	[2],[4],[10]	1.32%	1.32%
Credit And Equity Investments Primarily In Private Equity Owned Companies [Member]
Investment Securities [Line Items]
Carrying Value	[2],[11]	$ 3,721	$ 2,782
Unfunded Balance	[2],[11]	$ 1,662	$ 2,536
Percentage investment held by the entity	[2],[4],[11]	0.55%	0.98%

[1] At the fund manager’s discretion, the term of the fund may be extended for up to two additional one-year periods.

[2] Except under certain circumstances, withdrawals from the funds or any assignments are not permitted. Distributions, except income from late admission of a new limited partner, will be received when underlying investments of the funds are liquidated.

[3] The term is expected to be two years following the maturity of the fund’s outstanding leverage. Although the capital commitment period has expired, follow-on investments and pending commitments may require additional fundings.

[4] Represents the Company’s percentage investment in the fund at each balance sheet date.

[5] Effective July 1, 2023, this investment is in the process of winding down. Although the capital commitment period has ended, the general partner could still request an additional funding under certain circumstances.

[6] Expected to have a ten-year term. The capital commitment period has expired but the general partner may request additional funding for follow-on investment.

[7] With the consent of a supermajority of partners, the term of the fund may be extended for up to three additional one-year periods.

[8] Expected to have an eight-year term from the commencement date, which can be extended for up to two additional one-year periods with the consent of either the advisory committee or a majority of limited partners.

[9] The capital commitment period has ended but an additional funding may be requested.

[10] The term is expected to end November 27, 2027. The term may be extended for up to four additional one-year periods at the general partner’s discretion, and up to two additional one-year periods with the consent of the advisory committee.

[11] Expected to have an eight-year term after the final admission date. The term may be extended for an additional one-year period at the general partner’s discretion, and up to two additional one-year periods with the consent of either the advisory committee or a majority of limited partners.