Reinsurance - Premiums earned and life premiums and contract charges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Property and casualty insurance premiums
Reinsurance
Property and casualty insurance premiums earned	$ (289)	$ (260)	$ (836)	$ (756)
Life premiums
Reinsurance
Life premiums and contract charges	$ (68)	$ (76)	$ (200)	$ (221)