Sales and Other Operating Revenue - Transitional Arrangements (Details) - Accounting Standards Update 2014-09 [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2011
Contract with Customer, Timing of Satisfaction of Performance Obligation and Payment	We have entered into contractual arrangements where we license proprietary technology to customers related to the optimization process for operating LNG plants. The agreements typically provide for negotiated payments to be made at stated milestones. The payments are not directly related to our performance under the contract and are recorded as deferred revenue to be recognized as revenue when the customer can utilize and benefit from their right to use the license. Payments are received in installments over the construction period.
Revenue, Initial Application Period Cumulative Effect Transition, Description	The cumulative effect of applying the standard relates solely to certain licensing arrangements where revenue was previously recognized ($61 million in 2011, $146 million in 2015, and $44 million in 2017) based on contractual milestones. Under ASC Topic 606, such revenues are recognized when the customer has the ability to utilize and benefit from its right to use the license. As a result, such historically recognized revenues must be reversed through a cumulative effect adjustment and deferred until such time when the customer has the ability to utilize and benefit from the license. The cumulative effect adjustment relates to contracts that were not substantially completed at the date of implementation.
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue Recognition, Milestone Method, Revenue Recognized		$ 44	$ 146	$ 61