Parent Company - Guarantees (Details) - Parent Company - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Instuments and Warrants
Condensed Financial Statement
Aggregate balance	$ 39,745	$ 32,996
Subsidiary Lease Obligations
Condensed Financial Statement
Aggregate balance	$ 865	$ 925

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121555522&loc=d3e12069-110248

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