Investments - OTTI losses by asset type (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other-than-temporary impairment losses by asset type
Fixed income securities	$ (80)	$ (47)	$ (14)
Total credit losses by asset type	(82)	(47)	(14)
Commitments to fund commercial mortgage loans, bank loans and agent loans	2	0	0
Fixed income securities
Other-than-temporary impairment losses by asset type
Fixed income securities	(5)	(14)	(10)
Corporate
Other-than-temporary impairment losses by asset type
Fixed income securities	(1)	(7)	(2)
ABS
Other-than-temporary impairment losses by asset type
Fixed income securities	(2)	(4)	(3)
MBS
Other-than-temporary impairment losses by asset type
Fixed income securities	(2)	(3)	(5)
Mortgage loans
Other-than-temporary impairment losses by asset type
Net increases related to credit losses	(39)	0	0
Limited partnership interests
Other-than-temporary impairment losses by asset type
Limited partnership interests	(10)	(6)	(3)
Bank loans
Other-than-temporary impairment losses by asset type
Net increases related to credit losses	(28)	(26)	0
Agent loans
Other-than-temporary impairment losses by asset type
Net increases related to credit losses	$ 0	$ (1)	$ (1)