v3.26.1
Investments (Fair Value of Available-For-Sale Investments with Gross Unrealized Losses by Investment Type and Length of Time That Individual Securities Have Been in a Continuous Unrealized Loss Position) (Details) - USD ($)
$ in Millions
Mar. 31, 2026
Dec. 31, 2025
Debt Securities [Member]    
Schedule of Investments [Line Items]    
Less Than 12 Months, Fair Value $ 18,275 $ 4,214
Less Than 12 Months, Gross Unrealized Losses (217) (30)
Greater Than 12 Months, Fair Value 20,868 25,100
Greater Than 12 Months, Gross Unrealized Losses (1,660) (1,595)
Total, Fair Value 39,143 29,314
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss (1,877) (1,625)
U.S. Government and Agency Obligations [Member]    
Schedule of Investments [Line Items]    
Less Than 12 Months, Fair Value 1,076 500
Less Than 12 Months, Gross Unrealized Losses (10) (4)
Greater Than 12 Months, Fair Value 1,959 2,339
Greater Than 12 Months, Gross Unrealized Losses (158) (152)
Total, Fair Value 3,035 2,839
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss (168) (156)
State and Municipal Obligations [Member]    
Schedule of Investments [Line Items]    
Less Than 12 Months, Fair Value 1,402 523
Less Than 12 Months, Gross Unrealized Losses (27) (8)
Greater Than 12 Months, Fair Value 3,418 4,342
Greater Than 12 Months, Gross Unrealized Losses (235) (224)
Total, Fair Value 4,820 4,865
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss (262) (232)
Corporate Obligations [Member]    
Schedule of Investments [Line Items]    
Less Than 12 Months, Fair Value 11,495 2,661
Less Than 12 Months, Gross Unrealized Losses (130) (16)
Greater Than 12 Months, Fair Value 9,010 10,399
Greater Than 12 Months, Gross Unrealized Losses (569) (524)
Total, Fair Value 20,505 13,060
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss (699) (540)
U.S. Agency Mortgage-Backed Securities [Member]    
Schedule of Investments [Line Items]    
Less Than 12 Months, Fair Value 3,295 346
Less Than 12 Months, Gross Unrealized Losses (44) (1)
Greater Than 12 Months, Fair Value 5,195 6,665
Greater Than 12 Months, Gross Unrealized Losses (599) (597)
Total, Fair Value 8,490 7,011
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss (643) (598)
Non-U.S. Agency Mortgage-Backed Securities [Member]    
Schedule of Investments [Line Items]    
Less Than 12 Months, Fair Value 1,007 184
Less Than 12 Months, Gross Unrealized Losses (6) (1)
Greater Than 12 Months, Fair Value 1,286 1,355
Greater Than 12 Months, Gross Unrealized Losses (99) (98)
Total, Fair Value 2,293 1,539
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss $ (105) $ (99)