Investments (Securities in a gross unrealized loss position by ratings) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	$ 29,511	$ 6,065
Gross Unrealized Losses	4,056	112
U.S. Government, Government agencies and Government-sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	2,355	898
Gross Unrealized Losses	337	8
AAA
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,559	368
Gross Unrealized Losses	298	6
AA
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	4,327	875
Gross Unrealized Losses	817	17
A
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	6,615	1,516
Gross Unrealized Losses	749	23
BBB
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	13,226	1,812
Gross Unrealized Losses	1,621	42
Non-investment grade
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,429	596
Gross Unrealized Losses	$ 234	$ 16