Sales and Other Operating Revenue - Transitional Arrangements (Details)	6 Months Ended
Jun. 30, 2019
Contract with Customer, Timing of Satisfaction of Performance Obligation and Payment	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.

Description of effect, from relationship that timing of satisfaction of performance obligation has on timing of payment, on right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time and on obligation to transfer good or service to customer for which consideration from customer has been received or is due.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130550-203045

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration