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Business Segments (Concentration Risk) (Details) - Percentage of Consolidated Revenue - Customer concentration risk	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Coal Mining customer | Coal Mining customer
Segment Reporting Information [Line Items]
Percentage of Consolidated Revenue	43.00%	55.00%
NAMining customer | NAMining customer
Segment Reporting Information [Line Items]
Percentage of Consolidated Revenue	19.00%	19.00%

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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

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