Progress Collections and Deferred Income - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2017
Disaggregation of Revenue [Line Items]
Progress collections and deferred income (contract liabilities)	$ 1,765	$ 1,775	$ 2,038
Revenue recognized, included in contract liability	1,392	1,525
Progress collections
Disaggregation of Revenue [Line Items]
Progress collections and deferred income (contract liabilities)	1,600	1,456
Deferred income
Disaggregation of Revenue [Line Items]
Progress collections and deferred income (contract liabilities)	$ 165	$ 319

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130532-203044

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

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