Reinsurance - Premiums and future policy benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Insurance [Abstract]
Direct Premiums Earned	$ 42	$ 2,661	$ 1,424	$ 5,405
Assumed Premiums Earned	101	57	284	193
Ceded Premiums Earned	(31)	(30)	(101)	(123)
Premiums Earned, Net	112	2,688	1,607	5,475
Policyholder Benefits and Claims Incurred, Direct	385	3,025	2,404	6,481
Policyholder Benefits and Claims Incurred, Assumed	161	77	370	313
Policyholder Benefits and Claims Incurred, Ceded	(107)	(147)	(305)	(399)
Policyholder Benefits and Claims Incurred, Net	$ 439	$ 2,955	$ 2,469	$ 6,395