Revenue Recognition - Remaining Performance Obligations (Details) $ in Billions	3 Months Ended
Mar. 31, 2018 USD ($)
Revenue Recognition
Practical expedient, remaining performance obligations	true
Remaining performance obligations related to customer contracts that are unsatisfied or partially unsatisfied	$ 131

Indicates (true/false) whether practical expedient is elected not to disclose amount of transaction price allocated to remaining performance obligation and explanation of expected timing of revenue recognition, when contract has expected duration of one year or less or right to consideration corresponds directly to performance completed.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130558-203045

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130557-203045

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84173487&loc=SL51747714-108306

Name:	us-gaap_RevenuePracticalExpedientRemainingPerformanceObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration