Investments - Contractual Maturities of Available-for-Sale Investments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Amortized Cost
Due in one year or less	$ 428
Due after one year through five years	948
Due after five years through ten years	167
Due after ten years	361
Amortized Cost	1,904	$ 1,826
Estimated Fair Value
Due in one year or less	429
Due after one year through five years	974
Due after five years through ten years	169
Due after ten years	366
Estimated Fair Value	$ 1,938

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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