Investments (Securities in a gross unrealized loss position by ratings) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	$ 26,363	$ 6,065
Gross Unrealized Losses	2,842	112
U.S. Government, Government agencies and Government-sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	2,150	898
Gross Unrealized Losses	223	8
AAA
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,232	368
Gross Unrealized Losses	205	6
AA
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	4,078	875
Gross Unrealized Losses	581	17
A
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	5,454	1,516
Gross Unrealized Losses	493	23
BBB
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	11,806	1,812
Gross Unrealized Losses	1,111	42
Non-investment grade
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,643	596
Gross Unrealized Losses	$ 229	$ 16