Reinsurance - Business Divestitures Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2023 USD ($) reinsurer
Ceded Credit Risk [Line Items]
Number of reinsurer insolvency for making company responsible for administering reinsurance business (at least) \| reinsurer	1
John Hancock
Ceded Credit Risk [Line Items]
Assets held under trust under reinsurance agreement \| $	$ 879.4

Represents the number of reinsurer insolvency for making company responsible for administering reinsurance business.

No definition available.

Name:	tl_ReinsuranceAgreementNumberOfReinsurerInsolvency
Namespace Prefix:	tl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 825
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479383/944-825-50-1B

+ Details

Name:	us-gaap_CededCreditRiskLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the reinsurer's funds held on its behalf by the ceding insurer, including funds held in trust, under reinsurance treaties or contracts with the assuming insurer as security for the payment of the obligations thereunder.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(10))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

+ Details

Name:	us-gaap_FundsHeldUnderReinsuranceAgreementsAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_CededCreditRiskAxis=tl_JohnHancockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: