SPECIAL PURPOSE ENTITIES - Additional Information (Details) - GPS $ in Millions	1 Months Ended	12 Months Ended
Jan. 31, 2015 USD ($)	Jan. 31, 2016 item project
Variable Interest Entity
Number of natural gas-fired power plants \| project		2
Number of joint ventures \| item		2
Cash distributions to joint venture partner \| $	$ 25

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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