Investments (Contractual maturity) (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Investments [Abstract]
Due in one year or less, cost or amortized cost	$ 1,424	$ 1,392
Due after one year through five years, cost or amortized cost	11,048	11,318
Due after five years through ten years, cost or amortized cost	13,437	13,491
Due after ten years, cost or amortized cost	19,547	18,467
Cost or Amortized Cost	45,456	44,668
Due in one year or less, estimated fair value	1,418	1,389
Due after one year through five years, estimated fair value	10,836	11,214
Due after five years through ten years, estimated fair value	13,050	13,238
Due after ten years, estimated fair value	18,576	17,561
Estimated Fair Value	$ 43,880	$ 43,402