Investments - Past due commercial mortgage loans (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Past due commercial mortgage loans	$ 4,670	$ 4,664
Current
Financing Receivable, Past Due [Line Items]
Past due commercial mortgage loans	4,665	4,664
30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due commercial mortgage loans	2	0
60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due commercial mortgage loans	0	0
Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due commercial mortgage loans	$ 3	$ 0