Current Fair Value of Debt (Detail) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt		$ 294,784	$ 296,640
Debt, fair value		263,203	308,355
7.75% Subordinated Notes due 2045
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt	[1]	96,895	96,864
Debt, fair value	[1]	82,214	100,264
7.875% Subordinated Notes due 2047
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt	[2]	126,182	126,147
Debt, fair value	[2]	109,282	134,462
Margin borrowing facilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt		71,707	73,629
Debt, fair value		$ 71,707	$ 73,629

[1] As of March 31, 2020 and December 31, 2019, the carrying value and fair value of the 7.75% Subordinated Notes due 2045 is net of unamortized debt issuance cost of $3.1 million.

[2] As of March 31, 2020 and December 31, 2019, the carrying value and fair value of the 7.875% Subordinated Notes due 2047 are net of unamortized debt issuance cost of $3.8 million and $3.9 million, respectively.