Mortgage Loans by Property Type and Geographic Region (Detail) - USD ($) $ in Millions		Jun. 30, 2026	Dec. 31, 2025
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	[1]	$ 2,071.7	$ 2,109.5
Mortgage Loans, Percent of Total	[1]	100.00%	100.00%
New England
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 48.6	$ 49.9
Mortgage Loans, Percent of Total		2.30%	2.40%
Mid-Atlantic
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 156.1	$ 159.9
Mortgage Loans, Percent of Total		7.50%	7.60%
East North Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 268.1	$ 275.3
Mortgage Loans, Percent of Total		12.90%	13.10%
West North Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 120.9	$ 135.9
Mortgage Loans, Percent of Total		5.80%	6.40%
South Atlantic
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 540.2	$ 497.2
Mortgage Loans, Percent of Total		26.20%	23.50%
East South Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 87.8	$ 96.7
Mortgage Loans, Percent of Total		4.20%	4.60%
West South Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 183.9	$ 190.5
Mortgage Loans, Percent of Total		8.90%	9.00%
Mountain
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 239.7	$ 255.3
Mortgage Loans, Percent of Total		11.60%	12.10%
Pacific
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 426.4	$ 448.8
Mortgage Loans, Percent of Total		20.60%	21.30%
Apartment
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 636.9	$ 642.5
Mortgage Loans, Percent of Total		30.70%	30.50%
Industrial
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 644.7	$ 659.0
Mortgage Loans, Percent of Total		31.20%	31.20%
Office
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 278.5	$ 313.3
Mortgage Loans, Percent of Total		13.40%	14.90%
Retail
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 484.2	$ 467.0
Mortgage Loans, Percent of Total		23.40%	22.10%
Other Property
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount		$ 27.4	$ 27.7
Mortgage Loans, Percent of Total		1.30%	1.30%

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