Investments - Mortgage loans amortized cost by debt service coverage ratio distribution and year of origination (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost, net	$ 833	$ 821
Mortgage loans
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	839	827
Allowance	(6)	(6)
Amortized cost, net	833	821
Mortgage loans | 2017 and prior
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	125
Mortgage loans | 2018
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	106
Mortgage loans | 2019
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	239
Mortgage loans | 2020
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	51
Mortgage loans | 2021
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	217
Mortgage loans | Current
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	101
Below 1.0 | Mortgage loans
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	18	0
Below 1.0 | Mortgage loans | 2017 and prior
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	0
Below 1.0 | Mortgage loans | 2018
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	0
Below 1.0 | Mortgage loans | 2019
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	0
Below 1.0 | Mortgage loans | 2020
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	0
Below 1.0 | Mortgage loans | 2021
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	0
Below 1.0 | Mortgage loans | Current
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	18
1.0 - 1.25 | Mortgage loans
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	67	46
1.0 - 1.25 | Mortgage loans | 2017 and prior
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	35
1.0 - 1.25 | Mortgage loans | 2018
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	0
1.0 - 1.25 | Mortgage loans | 2019
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	0
1.0 - 1.25 | Mortgage loans | 2020
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	10
1.0 - 1.25 | Mortgage loans | 2021
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	0
1.0 - 1.25 | Mortgage loans | Current
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	22
1.26 - 1.50 | Mortgage loans
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	128	160
1.26 - 1.50 | Mortgage loans | 2017 and prior
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	13
1.26 - 1.50 | Mortgage loans | 2018
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	5
1.26 - 1.50 | Mortgage loans | 2019
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	103
1.26 - 1.50 | Mortgage loans | 2020
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	0
1.26 - 1.50 | Mortgage loans | 2021
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	0
1.26 - 1.50 | Mortgage loans | Current
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	7
Above 1.50 | Mortgage loans
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	626	$ 621
Above 1.50 | Mortgage loans | 2017 and prior
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	77
Above 1.50 | Mortgage loans | 2018
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	101
Above 1.50 | Mortgage loans | 2019
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	136
Above 1.50 | Mortgage loans | 2020
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	41
Above 1.50 | Mortgage loans | 2021
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	217
Above 1.50 | Mortgage loans | Current
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost before allowance	$ 54