Investments (Securities in a gross unrealized loss position by ratings) (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	$ 20,644	$ 27,338
Gross Unrealized Losses	2,286	3,040
U.S. Government, Government agencies and Government-sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,980	2,567
Gross Unrealized Losses	267	373
AAA
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,376	1,830
Gross Unrealized Losses	243	283
AA
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	3,827	4,257
Gross Unrealized Losses	623	730
A
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	5,025	6,340
Gross Unrealized Losses	440	582
BBB
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	7,758	11,548
Gross Unrealized Losses	639	980
Non-investment grade
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	678	796
Gross Unrealized Losses	$ 74	$ 92