Fair Value - Separate Accounts Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	$ 4,692	$ 4,881
Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	4,475	4,852
Recurring | Other Receivables
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	217	29
Cash and cash equivalents | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	254	188
Debt securities | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	3,739	4,099
Equity securities | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	2	2
Common/collective trusts | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	480	563
Level 1 | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	1,089	1,467
Level 1 | Cash and cash equivalents | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	5	2
Level 1 | Debt securities | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	1,084	1,465
Level 1 | Equity securities | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	0	0
Level 1 | Common/collective trusts | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	0	0
Level 2 | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	3,386	3,385
Level 2 | Cash and cash equivalents | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	249	186
Level 2 | Debt securities | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	2,655	2,634
Level 2 | Equity securities | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	2	2
Level 2 | Common/collective trusts | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	480	563
Level 3 | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	0	0
Level 3 | Cash and cash equivalents | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	0	0
Level 3 | Debt securities | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	0	0
Level 3 | Equity securities | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	0	0
Level 3 | Common/collective trusts | Recurring
Fair Value, Separate Account Investment [Line Items]
Separate accounts assets	$ 0	$ 0