Other Commitments And Contingencies Other Commitments and Contingencies (Expense and Insurance Recoveries) (Details) - USD ($) $ in Millions	3 Months Ended	4 Months Ended	16 Months Ended	19 Months Ended
Mar. 31, 2020	Dec. 31, 2018	Dec. 31, 2019	Mar. 31, 2020
Expense and Insurance Recoveries [Line Items]
Third-party claims	$ 0		$ 1,041	$ 1,041
Other incident-related costs	9		420	429
Total	9	$ 1,023	1,461	1,470
Insurance recoveries recorded	0		(800)	(800)
Total costs incurred	$ 9		$ 661	$ 670

The amount recovered from insurance. These recoveries reduce costs and losses that are reported as a separate line item under operating expenses.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

Name:	us-gaap_InsuranceRecoveries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration