REGULATORY MATTERS (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Regulatory Assets
Deferred construction accounting costs	$ 17,095	$ 10,521
Iatan1
Regulatory Assets
Deferred construction accounting costs	5,743	5,849
Iatan1 | Deferred Carrying Charges
Regulatory Assets
Deferred construction accounting costs	2,728	2,779
Iatan1 | Deferred O&M
Regulatory Assets
Deferred construction accounting costs	1,363	1,388
Iatan1 | Depreciation.
Regulatory Assets
Deferred construction accounting costs	1,652	1,682
Iatan2
Regulatory Assets
Deferred construction accounting costs	10,890	4,524
Iatan2 | Deferred Carrying Charges
Regulatory Assets
Deferred construction accounting costs	3,891	1,770
Iatan2 | Deferred O&M
Regulatory Assets
Deferred construction accounting costs	4,271	1,643
Iatan2 | Depreciation.
Regulatory Assets
Deferred construction accounting costs	2,728	1,111
Plum point
Regulatory Assets
Deferred construction accounting costs	462	148
Plum point | Deferred Carrying Charges
Regulatory Assets
Deferred construction accounting costs	65	33
Plum point | Deferred O&M
Regulatory Assets
Deferred construction accounting costs	239	70
Plum point | Depreciation.
Regulatory Assets
Deferred construction accounting costs	$ 158	$ 45