Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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.

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No definition available.

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Percentage of voting equity interests acquired at the acquisition date in the business combination.

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Amount of assets, excluding financial assets and goodwill, that lack physical substance, having a projected indefinite period of benefit, acquired at the acquisition date.

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The amount of identifiable intangible assets recognized as of the acquisition date.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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BUSINESS COMBINATIONS (Details) - USD ($)		9 Months Ended
BUSINESS COMBINATIONS (Details) - USD ($)	May 02, 2016	Sep. 30, 2016	Dec. 31, 2015
BUSINESS ACQUISITIONS
Payment to acquire business, net of cash acquired		$ 4,934,000
Goodwill		$ 193,655,000	$ 191,823,000
ESI
BUSINESS ACQUISITIONS
Percentage of outstanding shares acquired	100.00%
Payment to acquire business, net of cash acquired	$ 4,900,000
Goodwill	1,000,000
Identifiable intangible assets	$ 861,000
Weighted average amortization period	14 years
Indefinite-lived environmental permits	$ 638,000