Investments (Contractual maturity) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Investments [Abstract]
Due in one year or less, cost or amortized cost	$ 1,012	$ 1,603
Due after one year through five years, cost or amortized cost	9,880	10,637
Due after five years through ten years, cost or amortized cost	13,788	13,294
Due after ten years, cost or amortized cost	16,352	14,411
Cost or Amortized Cost	41,032	39,945
Due in one year or less, estimated fair value	1,001	1,624
Due after one year through five years, estimated fair value	9,399	11,229
Due after five years through ten years, estimated fair value	12,453	14,338
Due after ten years, estimated fair value	14,774	17,182
Estimated Fair Value	$ 37,627	$ 44,373