Investments - Schedule of Contractual Maturities of Investments (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Amortized cost
Due in one year or less	$ 600
Due after one year through five years	3,293
Due after five years through ten years	3,879
Due after ten years	3,501
Total	11,273	$ 11,108
Fair value
Due in one year or less	608
Due after one year through five years	3,500
Due after five years through ten years	4,212
Due after ten years	3,837
Total	$ 12,157	$ 11,698
% of fair value
Due in one year or less	5.00%
Due after one year through five years	28.80%
Due after five years through ten years	34.60%
Due after ten years	31.60%
Total	100.00%