Investments - Other-than-temporary impairment losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
OTTI losses
Gross	$ (10)	$ (3)	$ (23)	$ (5)
Included in OCI	2	(1)	3	(2)
Net	(8)	(4)	(20)	(7)
Municipal
OTTI losses
Gross	(2)	0	(2)	0
Included in OCI	2	0	2	0
Net	0	0	0	0
Corporate
OTTI losses
Gross	0	0	(1)	0
Included in OCI	0	0	(1)	0
Net	0	0	(2)	0
ABS
OTTI losses
Gross	0	0	(1)	0
Included in OCI	0	(1)	0	(1)
Net	0	(1)	(1)	(1)
RMBS
OTTI losses
Gross	0	0	0	(1)
Included in OCI	0	0	0	0
Net	0	0	0	(1)
CMBS
OTTI losses
Gross	(1)	(3)	(3)	(3)
Included in OCI	0	0	2	(1)
Net	(1)	(3)	(1)	(4)
Fixed income securities
OTTI losses
Gross	(3)	(3)	(7)	(4)
Included in OCI	2	(1)	3	(2)
Net	(1)	(4)	(4)	(6)
Limited partnership interests
OTTI losses
Gross	0	0	(2)	0
Included in OCI	0	0	0	0
Net	0	0	(2)	0
Other
OTTI losses
Gross	(7)	0	(14)	(1)
Included in OCI	0	0	0	0
Net	$ (7)	$ 0	$ (14)	$ (1)