Investments - Schedule of Contractual Maturities of Investments (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Amortized cost
Due in one year or less	$ 566
Due after one year through five years	3,187
Due after five years through ten years	3,811
Due after ten years	3,575
Total	11,139	$ 11,108
Fair value
Due in one year or less	574
Due after one year through five years	3,354
Due after five years through ten years	4,081
Due after ten years	3,902
Total	$ 11,911	$ 11,698
% of fair value
Due in one year or less	4.80%
Due after one year through five years	28.20%
Due after five years through ten years	34.30%
Due after ten years	32.70%
Total	100.00%