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Description of the Business and Summary of Significant Accounting Policies - Concentration of Credit Risk (Details) - Trade and Other Receivables - Customer Concentration Risk	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Customer A
Concentration Risk [Line Items]
Concentration risk, percentage	13.00%	14.00%
Customer B
Concentration Risk [Line Items]
Concentration risk, percentage	41.00%	23.00%

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- Definition

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

No definition available.

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- Definition

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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