Income Taxes Valuation Allowance, Additional Details (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Valuation Allowance, Deferred Tax Asset, Increase, Amount	$ 26			$ 56
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount		$ 30	$ (76)		$ (70)	$ (284)	$ 31

Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other adjustments.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Name:	us-gaap_IncomeTaxReconciliationOtherAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration