Financial Instruments - Contractual Maturities (Details) $ in Millions	Dec. 31, 2019 USD ($)
Amortized Cost
Due within one year	$ 35,064
Due after one year through five years	9,262
Due after five years through ten years	301
Due after ten years	680
Total	45,307
Estimated Fair Value
Due within one year	35,071
Due after one year through five years	9,304
Due after five years through ten years	302
Due after ten years	682
Total	$ 45,359