Amount of liability position for contract or contract feature in long-duration contract issued by insurance entity that both protects contract holder from other-than-nominal capital market risk and exposes insurance entity to other-than-nominal capital market risk.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 7B
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-7B

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29G
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-29G

Name:	us-gaap_MarketRiskBenefitLiabilityAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Long-Duration Insurance Contracts - Market Risk Benefits by Asset and Liability Balance (Details) - USD ($) $ in Millions	Sep. 30, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Market Risk Benefit [Line Items]
Net	$ (9.3)	$ (6.7)	$ (6.8)	$ (5.7)	$ (6.2)	$ (3.9)
Deferred variable annuities
Market Risk Benefit [Line Items]
(Asset)	(10.6)		(8.8)
Liability	1.2		2.0
Net	$ (9.3)		$ (6.8)