Reserve for Unpaid Losses and Loss Adjustment Expenses - GB Additional information (Details) - Group Benefits - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior incurral year development [1]	$ (265)	$ (242)
Disability Insurance Policy [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior incurral year development [1]	236	195
group life term, disability and accident [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior incurral year development [1]	19	40
Supplemental Health
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior incurral year development [1]	$ 10	$ 10