Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
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-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
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-Topic 944
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Name:	us-gaap_PolicyholderAccountBalanceLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Long-Duration Insurance Contracts - Reconciliation of Policyholder Account Balances to the Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Policyholder Account Balance [Line Items]
Policyholders' account balances	$ 5,076.4		$ 5,100.3
Indexed Universal Life
Policyholder Account Balance [Line Items]
Policyholders' account balances	82.3	$ 78.2	72.9	$ 65.2	$ 61.0	$ 57.8
Experience life
Policyholder Account Balance [Line Items]
Policyholders' account balances	56.5	57.4	58.0	59.4	60.1	61.2
Fixed Account Annuities
Policyholder Account Balance [Line Items]
Policyholders' account balances	4,495.1	4,495.9	4,508.4	4,509.5	4,519.9	4,556.0
Fixed Indexed Account Annuities
Policyholder Account Balance [Line Items]
Policyholders' account balances	388.6	399.7	409.5	426.6	437.4	449.0
SPIA (non-life contingent)
Policyholder Account Balance [Line Items]
Policyholders' account balances	27.9	$ 28.3	28.6	$ 30.4	$ 31.6	$ 32.6
Reconciling items
Policyholder Account Balance [Line Items]
Policyholders' account balances	$ 26.0		$ 22.9