Long-Duration Insurance Contracts - Separate Account Liability Rollforward (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2026	Jun. 30, 2025
Separate Account, Liability [Roll Forward]
Balance, beginning of year	$ 4,157.4
Balance, end of period	3,959.1
Variable Account Annuities
Separate Account, Liability [Roll Forward]
Balance, beginning of year	4,157.4	$ 3,708.8
Deposits	71.0	293.8
Withdrawals	(69.1)	(316.4)
Net transfers	(8.8)	(27.5)
Fees and charges	(15.1)	(57.2)
Market appreciation (depreciation)	(176.3)	555.9
Other	0.0	$ 0.0
Balance, end of period	$ 3,959.1

Amount of cash inflow to separate account liability for cash received for deposit.

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Amount of increase (decrease) in separate account liability from performance of investment.

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Amount increase (decrease) in separate account liability from change, classified as other.

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Amount of decrease in separate account liability from policy charge.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of decrease in liability for separate account from withdrawal of funds.

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Amount of liability for variable contract in which all or portion of contract holder's funds is allocated to specific separate account and supported by assets held in separate account.

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Amount of transfer to (from) liability for policyholder account balance (to) from liability for separate account.

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