Background and Basis of Presentation Background and Basis of Presentation (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Proceeds from issuance of commercial paper	$ 2,776	$ 5,518
Repayments of commercial paper	$ (1,453)	$ (6,354)

The cash outflow due to repaying amounts borrowed by issuing commercial paper.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3291-108585

Name:	us-gaap_RepaymentsOfCommercialPaper
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration