Marketable Securities and Held-to-Maturity Debt Securities - Contractual maturity (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Marketable securities by contractual maturity
Due in one year or less	$ 404
Due after one year through five years	15
Due after five years through ten years	15
Total marketable securities	$ 434	$ 141

Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year through fifth year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

No definition available.

Name:	us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant