FINANCIAL INSTRUMENTS - FINANCE OBLIGATION AND FINANCIAL INSTRUMENTS NOT CARRIED AT FAIR VALUE (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2014	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Finance obligation to ACB Energy Partners LLC		$ 19,659	$ 0
Carrying amount of long-term debt	[1]	1,009,400	1,035,848
Level 2 [Member]
Schedule of Equity Method Investments [Line Items]
Estimated fair value of long-term debt		1,058,500	1,079,000
Carrying amount of long-term debt		1,009,400	$ 1,035,800
Marina Energy LLC [Member] | Energenic US LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity interest			50.00%
Other construction costs		$ 23,700

[1] Long-term debt maturities and sinking funds requirements for the succeeding five years are as follows (in thousands): 2016, $29,454; 2017, $172,558; 2018,$40,667; 2019,$260,783; and 2020, $74,476.