Investments - Schedule of Company's Investments in Limited Partnerships (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021
Investment Securities [Line Items]
Carrying Value		$ 25,702	$ 28,133
Unfunded Balance		5,661	11,073
Private US Lower Middle Market Companies [Member]
Investment Securities [Line Items]
Carrying Value	[1],[2],[3]	4,146	6,076
Unfunded Balance	[1],[2],[3]	$ 0	$ 2,085
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]	$ 2,528	$ 3,423
Unfunded Balance	[1],[2],[5]	$ 0	$ 0
Percentage investment held by the entity	[1],[2],[4],[5]	1.66%	1.69%
Power Utility and Energy Industries and Infrastructure [Member]
Investment Securities [Line Items]
Carrying Value	[2],[6],[7]	$ 5,319	$ 6,270
Unfunded Balance	[2],[6],[7]	$ 0	$ 1,401
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]	$ 3,470	$ 4,437
Unfunded Balance	[2],[8],[9]	$ 0	$ 0
Percentage investment held by the entity	[2],[4],[8],[9]	0.56%	0.57%
Mature Real Estate Private Equity Funds And Portfolio Globally [Member]
Investment Securities [Line Items]
Carrying Value	[2],[10]	$ 7,457	$ 5,977
Unfunded Balance	[2],[10]	$ 3,125	$ 4,537
Percentage investment held by the entity	[2],[4],[10]	1.32%	1.36%
Credit And Equity Investments Primarily In Private Equity Owned Companies [Member]
Investment Securities [Line Items]
Carrying Value	[2],[11]	$ 2,782	$ 1,950
Unfunded Balance	[2],[11]	$ 2,536	$ 3,050
Percentage investment held by the entity	[2],[4],[11]	0.98%	0.47%

[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 the later of ten years or 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] The term has been extended for a second additional one-year period to June 30, 2023. 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.