FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Current	$ 66	$ 1,068
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Mining asset impairment	0	23,242	$ 0
Noncash goodwill impairment charge	0	36,571	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		40,346
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Property, Plant, and Equipment, Fair Value Disclosure		40,346
Goodwill, Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		0
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Property, Plant, and Equipment, Fair Value Disclosure		0
Goodwill, Fair Value Disclosure		0
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments for contractual obligations	9,480	9,840
Derivative Asset, Current	66	1,068
Preferred stock	250	250
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	(8)	(43)
Assets, Fair Value Disclosure	9,788	11,115
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Preferred stock	250	250
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments for contractual obligations	9,480	9,840
Derivative Asset, Current	0	0
Preferred stock	0	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure	9,480	9,840
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Preferred stock	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments for contractual obligations	0	0
Derivative Asset, Current	66	1,068
Preferred stock	0	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	(8)	(43)
Assets, Fair Value Disclosure	58	1,025
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Preferred stock	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments for contractual obligations	0	0
Derivative Asset, Current	0	0
Preferred stock	250	250	250
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure	250	250
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Preferred stock	250	250	$ 250
Gain (Loss) on Investments	$ 0	0
Impairment Charges, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Mining asset impairment		$ 59,813