Fair Value - Separate Accounts Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Separate Account Investment [Line Items]
Separate accounts liabilities	$ 3,334	$ 3,250	$ 3,200	$ 3,228
Separate accounts assets	3,334	3,250
Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	3,436	3,204
Recurring | Other Payables
Fair Value, Separate Account Investment [Line Items]
Separate accounts liabilities	102
Recurring | Other Receivables
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets		46
Recurring | Cash and cash equivalents
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	165	168
Recurring | Debt securities
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	899	2,507
Recurring | Common/collective trusts
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	2,372	529
Recurring | Level 1
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	203	560
Recurring | Level 1 | Cash and cash equivalents
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	1	2
Recurring | Level 1 | Debt securities
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	202	558
Recurring | Level 1 | Common/collective trusts
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	0	0
Recurring | Level 2
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	3,233	2,644
Recurring | Level 2 | Cash and cash equivalents
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	164	166
Recurring | Level 2 | Debt securities
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	697	1,949
Recurring | Level 2 | Common/collective trusts
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	2,372	529
Recurring | Level 3
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	0	0
Recurring | Level 3 | Cash and cash equivalents
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	0	0
Recurring | Level 3 | Debt securities
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	0	0
Recurring | Level 3 | Common/collective trusts
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	$ 0	$ 0