ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of net loss	$ 12,565	$ 8,542
Amortization of unrecognized prior service cost	(373)	(303)
Reclassification adjustment, before tax and regulatory adjustments	12,192	8,239
Regulatory adjustments	(11,964)	(13,756)
Reclassification adjustment, before tax	228	(5,517)
Reclassification adjustment, Tax	(88)	2,124
Reclassification adjustment, net of tax	$ 140	$ (3,393)

Other comprehensive income (loss) reclassification adjustment, before tax and regulatory adjustments

No definition available.

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- Definition

Other comprehensive income (loss) reclassification - Regulatory adjustments represent pension and other postretirement benefit costs expected to be recovered through rates and are deferred as part of our regulatory assets.

+ References

No definition available.

+ Details

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- Definition

The amount of gains or losses recognized in net periodic benefit cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(4)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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- Definition

The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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- Definition

Amount before tax of reclassification adjustment from accumulated other comprehensive (income) loss related to net period benefit cost (credit) for pension and other postretirement defined benefit plans.

+ References

No definition available.

+ Details

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- Definition

Amount after tax of reclassification adjustment from accumulated other comprehensive (income) loss related to net period benefit cost (credit) for pension and other postretirement defined benefit plans.

+ References

No definition available.

+ Details

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- Definition

Amount of tax (expense) benefit of reclassification adjustment from accumulated other comprehensive (income) loss related to pension and other postretirement defined benefit plans.

+ References

No definition available.

+ Details

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