Investment Gains and Losses Reported in Consolidated Statements of Income (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022		Jun. 30, 2021
Fixed Maturity Securities
Gross Gains on Sales	$ 0.5	$ 2.3	$ 0.8	[1]	$ 73.6
Gross Losses on Sales	(4.2)	(2.5)	(13.0)		(3.6)
Credit Losses	0.0	(1.0)	(4.1)		(9.3)
Mortgage Loans and Other Invested Assets
Gross Gains on Sales	0.0	1.0	1.4		3.5
Credit Losses	0.4	0.1	(0.1)		(1.6)
Embedded Derivative in Modified Coinsurance Arrangement	(0.8)	1.7	(4.2)		18.6
All Other Derivatives	3.7	(0.1)	5.5		1.6
Foreign Currency Transactions	(2.9)	(0.4)	(4.4)		(0.5)
Net Investment Gain (Loss)	$ (4.1)	$ 0.9	$ (17.9)		$ 85.5

[1] 1Gross gains on sales of fixed maturity securities for the six months ended June 30, 2021 includes gains of $67.6 million as a result of the second phase of the reinsurance transaction that we completed during the first quarter of 2021. See Note 12 for further discussion.