Fair Value - Separate Accounts Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	$ 3,200	$ 3,228
Separate accounts liabilities	3,200	3,228	$ 3,318	$ 5,087
Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	3,159	3,313
Recurring | Other Receivables
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	41
Recurring | Other Payables
Fair Value, Separate Account Investment [Line Items]
Separate accounts liabilities		85
Recurring | Cash and cash equivalents
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	153	156
Recurring | Debt securities
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	2,563	2,677
Recurring | Common/collective trusts
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	443	480
Recurring | Level 1
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	668	714
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	667	712
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	2,491	2,599
Recurring | Level 2 | Cash and cash equivalents
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	152	154
Recurring | Level 2 | Debt securities
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	1,896	1,965
Recurring | Level 2 | Common/collective trusts
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	443	480
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