Reinsurance and indemnification - Claims expense, life contract benefits and interest credited to contractholder funds (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Property and casualty insurance claims and claims expense (1) (2)
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ 128	$ (216)	$ (213)	$ (465)
Life contract benefits
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	15	(74)	(121)	(92)
Interest credited to contractholder funds
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	(7)	$ (6)	(19)	(14)
PG&E | Property and casualty insurance claims and claims expense (1) (2)
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ 330		330
Michigan Catastrophic Claim Association | Property and casualty insurance claims and claims expense (1) (2)
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred			$ 195	$ 205