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Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 3.

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Amount of transfers of assets measured on a recurring basis out of Level 3 of the fair value hierarchy into Level 2.

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Amount of transfers of net derivative assets (liabilities) measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 3.

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Amount of transfers of net derivative assets (liabilities) measured on a recurring basis out of Level 3 of the fair value hierarchy into Level 2.

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Fair Value Measurements - Transfers (Details) - Recurring Fair Value Measurements - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3, net derivative assets (liabilities)	$ 0.1		$ 0.1
Transfers out of Level 3 into Level 2, net derivative assets (liabilities)				$ 0.3
Available-for-sale \| Fixed maturities
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3	103.4		411.2	188.3
Transfers out of Level 3 into Level 2	44.2	$ 11.2	223.2	180.7
Available-for-sale \| States and political subdivisions
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3				12.0
Transfers out of Level 3 into Level 2		10.2		10.2
Available-for-sale \| Corporate debt securities
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3	82.2		171.7	176.3
Transfers out of Level 3 into Level 2	34.3		77.2
Available-for-sale \| Commercial mortgage-backed securities
Fair Value Hierarchy Levels Transfers
Transfers out of Level 3 into Level 2				10.2
Available-for-sale \| Collateralized debt obligations
Fair Value Hierarchy Levels Transfers
Transfers out of Level 3 into Level 2	9.9		146.0	139.3
Available-for-sale \| Other debt obligations
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3	$ 21.2		$ 239.5
Transfers out of Level 3 into Level 2		$ 1.0		21.0
Trading \| Fixed maturities
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3				$ 29.0