Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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EQUITY METHOD INVESTMENTS - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule Of Equity Method Investments [Line Items]
Contributions to acquire equity method investments			$ 0	$ 15,649,000
OGC
Schedule Of Equity Method Investments [Line Items]
Contributions to acquire equity method investments	$ 0		0
OGC and OCC
Schedule Of Equity Method Investments [Line Items]
Asset impairment	$ 12,300,000	$ 8,700,000	$ 12,300,000	$ 8,700,000
Principal Owner \| OGC
Schedule Of Equity Method Investments [Line Items]
Percentage of ownership interest	40.00%		40.00%