Investments - Schedule of Contractual Maturities of Investments (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Amortized cost
Due in one year or less	$ 971
Due after one year through five years	4,413
Due after five years through ten years	3,553
Due after ten years	5,772
Total	14,709	$ 14,361
Fair value
Due in one year or less	963
Due after one year through five years	4,300
Due after five years through ten years	3,427
Due after ten years	5,394
Total	$ 14,084	$ 13,791
% of fair value
Due in one year or less	6.80%
Due after one year through five years	30.50%
Due after five years through ten years	24.30%
Due after ten years	38.40%
Total	100.00%