SPECIAL PURPOSE ENTITIES - Additional Information (Details) - GPS	12 Months Ended
Jan. 31, 2017 item project
Variable Interest Entity
Number of natural gas-fired power plants \| project	2
Number of joint ventures \| item	2

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.

No definition available.

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Data Type:	xbrli:stringItemType
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Period Type:	duration