VARIABLE INTEREST ENTITIES (Details)	3 Months Ended
	Mar. 31, 2014 MW
UPPCO
Variable interest entity
Obligations to purchase energy under power purchase agreement (in megawatts)	0
Contracted capacity under a power purchase agreement (in megawatts)	17.5
AMP Trillium LLC | ITF
Variable interest entity
Variable interest entity ownership interest (as a percent)	30.00%
AMP Trillium LLC | Other venturer's ownership
Variable interest entity
Variable interest entity ownership interest (as a percent)	70.00%
EVO Trillium LLC | ITF
Variable interest entity
Variable interest entity ownership interest (as a percent)	15.00%
EVO Trillium LLC | Other venturer's ownership
Variable interest entity
Variable interest entity ownership interest (as a percent)	85.00%