Investments - Amortized cost, gross unrealized gains and losses and fair value for fixed income securities (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Schedule of Available for Sale Securities
Amortized cost, net	$ 47,904	$ 45,370
Gross unrealized, Gains	103	92
Gross unrealized, Losses	(2,457)	(2,977)
Fixed income securities	45,550	42,485
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost, net	7,957	8,123
Gross unrealized, Gains	3	6
Gross unrealized, Losses	(231)	(231)
Fixed income securities	7,729	7,898
Municipal
Schedule of Available for Sale Securities
Amortized cost, net	7,069	6,500
Gross unrealized, Gains	34	36
Gross unrealized, Losses	(263)	(326)
Fixed income securities	6,840	6,210
Corporate
Schedule of Available for Sale Securities
Amortized cost, net	30,801	28,562
Gross unrealized, Gains	63	46
Gross unrealized, Losses	(1,910)	(2,345)
Fixed income securities	28,954	26,263
Foreign government
Schedule of Available for Sale Securities
Amortized cost, net	1,075	997
Gross unrealized, Gains	0	0
Gross unrealized, Losses	(31)	(40)
Fixed income securities	1,044	957
ABS
Schedule of Available for Sale Securities
Amortized cost, net	1,002	1,188
Gross unrealized, Gains	3	4
Gross unrealized, Losses	(22)	(35)
Fixed income securities	$ 983	$ 1,157