Financial Instruments - Contractual Maturities (Details) $ in Millions	Jun. 30, 2020 USD ($)
Amortized Cost
Due within one year	$ 42,733
Due after one year through five years	15,671
Due after five years through ten years	654
Due after ten years	2,710
Cash Equivalents and Marketable Fixed Income Securities, Cost	61,768
Estimated Fair Value
Due within one year	42,746
Due after one year through five years	15,956
Due after five years through ten years	656
Due after ten years	2,723
Cash Equivalents and Marketable Fixed Income Securities, Fair Value	$ 62,081