Investments - Contractual Maturities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost
Due in one year or less	$ 665
Due after one year through five years	1,667
Due after five years through ten years	335
Due after ten years	541
Amortized Cost	3,208	$ 1,826
Estimated Fair Value
Due in one year or less	667
Due after one year through five years	1,662
Due after five years through ten years	335
Due after ten years	538
Amortized Cost	$ 3,202	$ 1,875