Revenue (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($) customer	Dec. 31, 2017 USD ($) customer	Dec. 31, 2016 customer
Concentration Risk [Line Items]
Revenue, information used to assess variable consideration constraint, adjustment for quality and transportation	18.00%	21.00%	26.00%
Number of customers \| customer	2	3	3
Contract with customer, asset, net, current \| $	$ 4.2	$ 11.1
Revenue from Contract with Customer \| Product Concentration Risk
Concentration Risk [Line Items]
Sales to each significant customer as % of oil and gas sales	99.91734%	99.00%	99.00%

Revenue, Information Used To Assess Variable Consideration Constraint, Adjustment For Quality And Transportation

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- Definition

Revenue Recognition, Number Of Customers Production Sold To

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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