FINANCIAL INSTRUMENTS (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Schedule of Financial Instruments [Line Items]
Restricted investments held in escrow	$ 100,000	$ 100,000
Margin accounts with selected counterparties to support risk management activities	800,000	500,000
Restricted investments, energy-related contracts	200,000	0
Long-term receivables, net of unamortized discount		15,000,000
Estimated fair value of long-term debt	531,300,000	486,500,000
Carrying amount of long-term debt	505,000,000	475,000,000
Financing Receivable [Member]
Schedule of Financial Instruments [Line Items]
Long-term receivables, net of unamortized discount	15,000,000
Imputed interest	$ 1,300,000	$ 1,300,000