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ACQUISITIONS AND DISPOSITIONS - Purchase Price Allocation - Vibrant Energy (Details) - USD ($) $ in Thousands		18 Months Ended
	Apr. 07, 2016	Sep. 30, 2017	Dec. 31, 2016
Purchase price allocation:
Goodwill		$ 63,969	$ 62,873
Vibrant Energy
Purchase price allocation:
Cash	$ 136
Prepayments and other assets	636
Property, plant and equipment	7,321
Goodwill	3,279
Accounts payable and accrued liabilities	(5,179)
Net assets acquired	6,193
Consideration Transferred
Total consideration	$ 6,193
Cash consideration		4,900
Contingent Consideration		$ 1,300