Investments (Contractual maturity) (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Investments [Abstract]
Due in one year or less, cost or amortized cost	$ 1,392	$ 1,761
Due after one year through five years, cost or amortized cost	11,318	11,678
Due after five years through ten years, cost or amortized cost	13,491	13,134
Due after ten years, cost or amortized cost	18,467	16,908
Cost or Amortized Cost	44,668	43,481
Due in one year or less, estimated fair value	1,389	1,753
Due after one year through five years, estimated fair value	11,214	11,403
Due after five years through ten years, estimated fair value	13,238	12,415
Due after ten years, estimated fair value	17,561	15,540
Estimated Fair Value	$ 43,402	$ 41,111