Investments - Schedule of Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value for Fixed Income Securities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Schedule of Available for Sale Securities
Amortized cost, net	$ 49,649	$ 45,370
Gross unrealized gains	650	92
Gross unrealized losses	(1,434)	(2,977)
Fixed income securities	48,865	42,485
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost, net	8,624	8,123
Gross unrealized gains	114	6
Gross unrealized losses	(119)	(231)
Fixed income securities	8,619	7,898
Municipal
Schedule of Available for Sale Securities
Amortized cost, net	6,049	6,500
Gross unrealized gains	109	36
Gross unrealized losses	(152)	(326)
Fixed income securities	6,006	6,210
Corporate
Schedule of Available for Sale Securities
Amortized cost, net	31,951	28,562
Gross unrealized gains	397	46
Gross unrealized losses	(1,143)	(2,345)
Fixed income securities	31,205	26,263
Foreign government
Schedule of Available for Sale Securities
Amortized cost, net	1,286	997
Gross unrealized gains	17	0
Gross unrealized losses	(13)	(40)
Fixed income securities	1,290	957
ABS
Schedule of Available for Sale Securities
Amortized cost, net	1,739	1,188
Gross unrealized gains	13	4
Gross unrealized losses	(7)	(35)
Fixed income securities	$ 1,745	$ 1,157