Commitment and Contingencies (Severance) (Details) - Employee Severance - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Severance Liability [Line Items]
Postemployment Benefits Liability, Current	$ 20	$ 585	$ 283
Postemployment Benefits, Period Expense		652
Payments for Postemployment Benefits	(84)	(395)
SeveranceAccrualPreexistingIncreaseDecrease	$ (179)	$ 328

For a classified balance sheet, the carrying amount as of the balance sheet date of the portion of the obligations recognized for the various benefits provided to former or inactive employees, their beneficiaries, and covered dependents after employment but before retirement that is payable within one year of the balance sheet date.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 712
-SubTopic 10
-Section 25
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6410138&loc=d3e79691-111665

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.20)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 712
-SubTopic 10
-Section 25
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6410138&loc=d3e79708-111665

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