Reinsurance - Premiums earned and life premiums and contract charges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Property and casualty insurance premiums
Reinsurance
Property and casualty insurance premiums earned	$ (287)	$ (257)	$ (547)	$ (496)
Life premiums
Reinsurance
Life premiums and contract charges	$ (69)	$ (73)	$ (132)	$ (145)