Commitments - Standby and Commercial Letters of Credit (Details) - Financial Standby Letter of Credit $ in Millions	Sep. 30, 2019 USD ($)
Line of Credit Facility [Line Items]
Commitments	$ 2,219
Less Than One Year From The Balance Sheet Date
Line of Credit Facility [Line Items]
Commitments	1,124
More than One and within Five Years from Balance Sheet Date
Line of Credit Facility [Line Items]
Commitments	1,056
More than Five Years from Balance Sheet Date
Line of Credit Facility [Line Items]
Commitments	$ 39

Fair value portion of arrangements with third parties, including, but not limited to, operating lease arrangement and arrangement in which the entity has agreed to expend funds to procure goods or services, or has agreed to commit resources to supply goods or services.

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(25))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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