Investments - Amortized Cost Basis of Mortgage Loans for Each Credit Quality Indicator by Year of Origination (Details) - Commercial mortgage-backed $ in Millions	Sep. 30, 2023 USD ($)
Credit Quality Information [Abstract]
2023	$ 75
2022	248
2021	81
2020	135
2019	182
Prior	309
Total	1,030
DSCR Greater than or Equal to 1.6x, LTV Less than 55%
Credit Quality Information [Abstract]
2023
2022	9
2021	8
2020	97
2019	61
Prior	242
Total	417
DSCR Greater than or Equal to 1.6x, LTV 55% to 65%
Credit Quality Information [Abstract]
2023
2022
2021	5
2020
2019	8
Prior
Total	13
DSCR Greater than or Equal to 1.6x, LTV Greater than 65%
Credit Quality Information [Abstract]
2023
2022	31
2021	11
2020
2019
Prior
Total	42
DSCR Between 1.2 to 1.6x, LTV Less than 55%
Credit Quality Information [Abstract]
2023	28
2022	5
2021
2020	14
2019	29
Prior	28
Total	104
DSCR Between 1.2 to 1.6x, LTV 55% to 65%
Credit Quality Information [Abstract]
2023	15
2022	36
2021	36
2020	24
2019
Prior	32
Total	143
DSCR Between 1.2 to 1.6x, LTV Greater than 65%
Credit Quality Information [Abstract]
2023
2022	65
2021
2020
2019
Prior
Total	65
DSCR Less than or Equal to 1.2x, LTV Less than 55%
Credit Quality Information [Abstract]
2023	22
2022	34
2021
2020
2019
Prior
Total	56
DSCR Less than or Equal to 1.2x, LTV 55 to 65%
Credit Quality Information [Abstract]
2023	10
2022	41
2021
2020
2019	43
Prior
Total	94
DSCR Less than or Equal to 1.2x, LTV Greater than 65%
Credit Quality Information [Abstract]
2023
2022	27
2021	21
2020
2019	41
Prior	7
Total	$ 96