INTANGIBLES - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2011
INTANGIBLE ASSETS:
Amortization of intangible asset	$ 7,324	$ 7,324	$ 7,324
Future amortization of intangible assets
Intangible assets, net	25,634	32,958
Purchase Power Agreement
INTANGIBLE ASSETS:
Amortization of intangible asset	$ 7,300	$ 7,300	$ 7,300
Intangible asset, remaining life (in years)	4 years
Future amortization of intangible assets
2016	$ 7,324
2017	7,324
2018	7,324
2019	3,662
Intangible assets, net	$ 25,634
TCP | Purchase Power Agreement
INTANGIBLE ASSETS:
Intangible asset				$ 55,500