Stockholders' Equity - Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Reclassifications out of Accumulated Other Comprehensive Income [Line Items]
Interest and sundry (income) expense	$ (130)	$ (8)
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	$ 11

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=115205541&loc=SL114868664-224227

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