Amounts Recorded for Margin Borrowing Facilities and Subordinated Notes (Detail) - USD ($) $ in Thousands		Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Net carrying amount		$ 0	$ 126,430
7.875% Subordinated Notes due 2047
Debt Instrument [Line Items]
Outstanding principal			130,000
Unamortized debt issuance costs			(3,600)
Net carrying amount	[1]	$ 0	$ 126,430	[2]

[1] As of December 31, 2021, the carrying value and fair value of the 7.875% Subordinated Notes due 2047 are net of unamortized debt issuance cost of $3.6 million. In April 2022, the Company redeemed all of its outstanding 7.875% subordinated notes due 2047 and unamortized debt issuance cost of $3.5 million was written off and included in the consolidated statements of operations as loss on extinguishment of debt.

[2] Amounts outstanding at December 31, 2021 represent outstanding principal of $130.0 million, net of unamortized debt costs of $3.6 million