Investments (Contractual maturity) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Investments [Abstract]
Due in one year or less, cost or amortized cost	$ 1,533	$ 1,603
Due after one year through five years, cost or amortized cost	10,206	10,637
Due after five years through ten years, cost or amortized cost	14,040	13,294
Due after ten years, cost or amortized cost	15,143	14,411
Cost or Amortized Cost	40,922	39,945
Due in one year or less, estimated fair value	1,546	1,624
Due after one year through five years, estimated fair value	10,337	11,229
Due after five years through ten years, estimated fair value	14,032	14,338
Due after ten years, estimated fair value	16,024	17,182
Estimated Fair Value	$ 41,939	$ 44,373