Debt - Availability Under Revolving Credit Facilities (Details) $ in Millions	Sep. 30, 2019 USD ($)
Line of Credit Facility [Line Items]
Availability under revolving credit facilities	$ 3,106
2018 Unsecured Revolving Credit Facility
Line of Credit Facility [Line Items]
Availability under revolving credit facilities	2,650
Other revolving credit facilities
Line of Credit Facility [Line Items]
Availability under revolving credit facilities	$ 456

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant