REGULATORY MATTERS (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Regulatory Assets
Deferred construction accounting costs	$ 16,717	$ 17,095
Iatan1
Regulatory Assets
Deferred construction accounting costs	5,639	5,743
Iatan1 | Deferred Carrying Charges
Regulatory Assets
Deferred construction accounting costs	2,678	2,728
Iatan1 | Deferred O&M
Regulatory Assets
Deferred construction accounting costs	1,339	1,363
Iatan1 | Depreciation
Regulatory Assets
Deferred construction accounting costs	1,622	1,652
Iatan2
Regulatory Assets
Deferred construction accounting costs	10,661	10,890
Iatan2 | Deferred Carrying Charges
Regulatory Assets
Deferred construction accounting costs	3,821	3,891
Iatan2 | Deferred O&M
Regulatory Assets
Deferred construction accounting costs	4,155	4,271
Iatan2 | Depreciation
Regulatory Assets
Deferred construction accounting costs	2,685	2,728
Plum point
Regulatory Assets
Deferred construction accounting costs	417	462
Plum point | Deferred Carrying Charges
Regulatory Assets
Deferred construction accounting costs	64	65
Plum point | Deferred O&M
Regulatory Assets
Deferred construction accounting costs	195	239
Plum point | Depreciation
Regulatory Assets
Deferred construction accounting costs	$ 158	$ 158