Investment Gains and Losses Reported in Consolidated Statements of Income (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2025		Dec. 31, 2024	Dec. 31, 2023
Fixed Maturity Securities
Debt Securities, Available-for-sale, Realized Gain		$ 140.9	[1]	$ 1.3	$ 4.4
Gross Losses on Sales		(99.4)	[1]	(39.5)	(53.1)
Impairement Loss		(160.9)	[1]	(2.5)	0.0
Change in Allowance for Credit Losses	[2]	(3.1)		(3.0)	(2.2)
Mortgage Loans and Other Invested Assets
Gross Gains on Sales		14.4		0.5	6.0
Gross Losses on Sales		(2.1)		0.0	(1.0)
Impairment Loss		(5.6)		(7.0)	(3.0)
Credit Losses		0.2		(5.9)	(0.9)
Gain (Loss) on Embedded Derivative		6.3		13.0	12.4
All Other Derivatives		(2.9)		3.8	(0.6)
Gain (Loss) on Sale of Other Investments		0.2		9.2	0.0
Foreign Currency Transactions		5.4		(4.5)	2.0
Net Investment Loss		$ (106.6)		$ (34.6)	$ (36.0)

[1] Our investment gains and losses on fixed maturity securities for the year ended December 31, 2025 were driven primarily by the Closed Block long-term care and Unum US individual disability reinsurance transaction (Fortitude Re reinsurance transaction) which resulted in a net loss of $46.8 million. In addition, for the year ended December 31, 2025, we realized a $19.1 million loss on sales of fixed maturity securities relating to funding of a dividend from one of our subsidiaries.

[2] ncludes reduction of allowance on securities sold or otherwise disposed during the period.