Reserve for Unpaid Losses and Loss Adjustment Expenses - GB Additional information (Details) - Group Benefits - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior incurral year development [1]	$ (339)	$ (265)
Disability Insurance Policy [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior incurral year development [1]	282	236
group life term, disability and accident [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior incurral year development [1]	$ 56	19
Supplemental Health
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior incurral year development [1]		$ 10

Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-3

Name:	us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration