Investments - Realized capital gains and losses by asset type (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Realized capital gains and losses by asset type
Realized capital gains (losses)	$ 4	$ 1,356	$ 1,885	$ (877)
Fixed income securities
Realized capital gains and losses by asset type
Realized capital gains (losses)		983	461	(237)
Equity securities
Realized capital gains and losses by asset type
Realized capital gains (losses)		346	1,210	(594)
Mortgage loans
Realized capital gains and losses by asset type
Realized capital gains (losses)		(47)	0	2
Limited partnership interests
Realized capital gains and losses by asset type
Realized capital gains (losses)		24	200	(101)
Derivatives
Realized capital gains and losses by asset type
Realized capital gains (losses)		53	(15)	46
Other
Realized capital gains and losses by asset type
Realized capital gains (losses)		$ (3)	$ 29	$ 7