Investments - Other-than-temporary impairment losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other-than-temporary impairment losses
Total other-than-temporary impairment (“OTTI”) losses	$ (2)	$ (13)	$ (2)	$ (41)
Included in OCI	0	0	(1)	4
Net OTTI losses recognized in earnings	(2)	(13)	(3)	(37)
Municipal
Other-than-temporary impairment losses
Total other-than-temporary impairment (“OTTI”) losses	0	(1)	0	(1)
Included in OCI	0	0	0	0
Net OTTI losses recognized in earnings	0	(1)	0	(1)
Corporate
Other-than-temporary impairment losses
Total other-than-temporary impairment (“OTTI”) losses			0	(7)
Included in OCI			0	3
Net OTTI losses recognized in earnings			0	(4)
RMBS
Other-than-temporary impairment losses
Total other-than-temporary impairment (“OTTI”) losses	(1)	0	(1)	0
Included in OCI	0	0	0	(2)
Net OTTI losses recognized in earnings	(1)	0	(1)	(2)
CMBS
Other-than-temporary impairment losses
Total other-than-temporary impairment (“OTTI”) losses	0	(3)	0	(9)
Included in OCI	0	0	(1)	3
Net OTTI losses recognized in earnings	0	(3)	(1)	(6)
Fixed income securities
Other-than-temporary impairment losses
Total other-than-temporary impairment (“OTTI”) losses	(1)	(4)	(1)	(17)
Included in OCI	0	0	(1)	4
Net OTTI losses recognized in earnings	(1)	(4)	(2)	(13)
Equity securities
Other-than-temporary impairment losses
Total other-than-temporary impairment (“OTTI”) losses	0	(5)	0	(15)
Included in OCI	0	0	0	0
Net OTTI losses recognized in earnings	0	(5)	0	(15)
Limited partnership interests
Other-than-temporary impairment losses
Total other-than-temporary impairment (“OTTI”) losses	0	(4)	0	(7)
Included in OCI	0	0	0	0
Net OTTI losses recognized in earnings	0	(4)	0	(7)
Other
Other-than-temporary impairment losses
Total other-than-temporary impairment (“OTTI”) losses	(1)	0	(1)	(2)
Included in OCI	0	0	0	0
Net OTTI losses recognized in earnings	$ (1)	$ 0	$ (1)	$ (2)