FAIR VALUE MEASUREMENTS (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) item	Sep. 30, 2016 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of Rabbit Trusts established | item			2
Net gains of the Rabbi Trust investments			$ 1,950,000	$ 1,379,000
Unrealized net gains (losses) of the Rabbi Trust investments			1,424,000	273,000
Losses on impairment of long-lived assets	$ 0	$ 0	0	10,506,000
Nonrecurring [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets subject to fair value measurement on a nonrecurring basis	$ 0	$ 0	$ 0	$ 0