SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Electric Revenue	$ 1,076,725	$ 1,022,728	$ 1,033,052
Revenue, Net	1,080,662	1,026,756	1,036,029
Operating Income (Loss)	242,602	155,352	191,811
Total other income	24,364	27,802	18,984
Other Interest and Dividend Income	2,279	2,303	3,040
Earnings (Losses) of Unconsolidated Equity-Method Investments	(328)	798	3,008
Interest Expense	73,869	71,526	75,114
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	195,047	114,729	141,729
Income Tax Expense (Benefit)	26,113	(52,133)	(731)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	168,934	166,862	142,460
Net Income (Loss) Attributable to Parent	168,761	166,693	142,798
Assets	5,319,516	4,960,609	4,676,055
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets	239,788	337,770	338,252
Reportable Segment [Member]
Segment Reporting Information [Line Items]
Electric Revenue	1,076,725	1,022,728	1,033,052
Operating Income (Loss)	242,179	155,470	193,514
Total other income	23,996	27,772	18,361
Other Interest and Dividend Income	1,980	2,146	2,116
Earnings (Losses) of Unconsolidated Equity-Method Investments	9,412	9,018	11,281
Interest Expense	73,429	71,055	73,925
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	204,138	123,351	151,347
Income Tax Expense (Benefit)	35,970	(41,399)	10,713
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	168,168	164,750	140,634
Assets	5,215,711	4,856,839	4,568,393
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets	239,761	337,765	338,252
All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue, Net	3,937	4,028	2,977
Operating Income (Loss)	423	(118)	(1,703)
Total other income	368	30	623
Other Interest and Dividend Income	380	233	1,023
Earnings (Losses) of Unconsolidated Equity-Method Investments	(9,740)	(8,220)	(8,273)
Interest Expense	521	547	1,288
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	(9,091)	(8,622)	(9,618)
Income Tax Expense (Benefit)	(9,857)	(10,734)	(11,444)
Net Income (Loss) Attributable to Parent	593	1,943	2,164
Assets	115,748	122,678	131,553
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets	27	5	0
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenue, Net	0	0	0
Operating Income (Loss)	0	0	0
Total other income	0	0	0
Other Interest and Dividend Income	(81)	(76)	(99)
Earnings (Losses) of Unconsolidated Equity-Method Investments	0	0	0
Interest Expense	(81)	(76)	(99)
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	0	0	0
Income Tax Expense (Benefit)	0	0	0
Net Income (Loss) Attributable to Parent	0	0	0
Assets	(11,943)	(18,908)	(23,891)
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets	0	0	0
Idaho Power Company
Segment Reporting Information [Line Items]
Electric Revenue	1,076,725	1,022,728	1,033,052
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	33.00%
Operating Income (Loss)	250,704	164,366	200,308
Total other income	26,863	30,040	24,964
Earnings (Losses) of Unconsolidated Equity-Method Investments	9,412	9,018	11,281
Interest Expense	73,429	71,055	73,925
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	204,138	123,351	151,347
Income Tax Expense (Benefit)	35,970	(41,399)	10,713
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	168,168	164,750	140,634
Assets	$ 5,215,711	$ 4,856,839