Stockholders' Equity - Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassifications out of Accumulated Other Comprehensive Income [Line Items]
Interest and sundry (income) expense	$ (29)	$ 24	$ (222)	$ 106
Reclassification out of Accumulated Other Comprehensive Income \| Pension and postretirement benefits, pre-tax
Reclassifications out of Accumulated Other Comprehensive Income [Line Items]
Interest and sundry (income) expense	$ 21		$ 43

The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).

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 210.5-03.7)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

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