Mortgage Loans by Property Type and Geographic Region (Detail) - USD ($) $ in Millions		Mar. 31, 2026	Dec. 31, 2025
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	[1]	$ 2,066.3	$ 2,109.5
Mortgage Loans, Percent of Total	[1]	100.00%	100.00%
New England
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 49.2	$ 49.9
Mortgage Loans, Percent of Total		2.40%	2.40%
Mid-Atlantic
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 158.0	$ 159.9
Mortgage Loans, Percent of Total		7.60%	7.60%
East North Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 270.0	$ 275.3
Mortgage Loans, Percent of Total		13.10%	13.10%
West North Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 134.6	$ 135.9
Mortgage Loans, Percent of Total		6.50%	6.40%
South Atlantic
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 499.9	$ 497.2
Mortgage Loans, Percent of Total		24.20%	23.50%
East South Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 88.6	$ 96.7
Mortgage Loans, Percent of Total		4.30%	4.60%
West South Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 185.8	$ 190.5
Mortgage Loans, Percent of Total		9.00%	9.00%
Mountain
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 235.1	$ 255.3
Mortgage Loans, Percent of Total		11.40%	12.10%
Pacific
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 445.1	$ 448.8
Mortgage Loans, Percent of Total		21.50%	21.30%
Apartment
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 634.0	$ 642.5
Mortgage Loans, Percent of Total		30.70%	30.50%
Industrial
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 650.9	$ 659.0
Mortgage Loans, Percent of Total		31.50%	31.20%
Office
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 283.4	$ 313.3
Mortgage Loans, Percent of Total		13.70%	14.90%
Retail
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 470.4	$ 467.0
Mortgage Loans, Percent of Total		22.80%	22.10%
Other Property
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 27.6	$ 27.7
Mortgage Loans, Percent of Total		1.30%	1.30%

[1] 1Loan-to-Value Ratio utilizes the most recent internal valuation of the property