Revenue Recognition - Remaining Performance Obligations (Details) - USD ($) $ in Billions	6 Months Ended	12 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Revenue Recognition
Practical expedient, remaining performance obligations	true	true
Remaining performance obligations related to customer contracts that are unsatisfied or partially unsatisfied	$ 119	$ 124

Indicates (true false) whether optional exemption was applied not to disclose amount of transaction price allocated to and explanation of expected timing of revenue recognition for remaining performance obligation, 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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130558-203045

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