BENEFIT PLANS: Level 4 (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Defined Benefit Plan Disclosure
Net periodic benefit cost recognized for financial reporting					$ 15,204,000		$ 9,897,000
Pension Plan
Defined Benefit Plan Disclosure
Service cost	6,345,000		5,074,000		12,786,000		10,239,000
Interest cost	7,853,000		7,610,000		15,745,000		15,161,000
Expected return on plan assets	(8,155,000)		(7,984,000)		(15,867,000)		(15,935,000)
Amortization of transition obligation	0		0		0		0
Amortization of prior service cost	86,000		129,000		173,000		259,000
Amortization of net loss	3,594,000		2,243,000		7,057,000		4,337,000
Net periodic benefit cost	9,723,000		7,072,000		19,894,000		14,061,000
Costs not recognized due to the effects of regulation	(4,954,000)	[1]	(4,350,000)	[1]	(10,343,000)	[1]	(9,610,000)	[1]
Net periodic benefit cost recognized for financial reporting	4,769,000	[1]	2,722,000	[1]	9,551,000	[1]	4,451,000	[1]
Contributions made to the defined benefit pension plan					34,000,000
Senior Management Security Plan
Defined Benefit Plan Disclosure
Service cost	538,000		488,000		1,076,000		976,000
Interest cost	804,000		773,000		1,609,000		1,546,000
Expected return on plan assets	0		0		0		0
Amortization of transition obligation	0		0		0		0
Amortization of prior service cost	54,000		61,000		107,000		122,000
Amortization of net loss	382,000		323,000		764,000		646,000
Net periodic benefit cost	1,778,000		1,645,000		3,556,000		3,290,000
Costs not recognized due to the effects of regulation	0	[1]	0	[1]	0	[1]	0	[1]
Net periodic benefit cost recognized for financial reporting	1,778,000	[1]	1,645,000	[1]	3,556,000	[1]	3,290,000	[1]
Postretirement Benefits
Defined Benefit Plan Disclosure
Service cost	295,000		290,000		646,000		662,000
Interest cost	749,000		824,000		1,567,000		1,717,000
Expected return on plan assets	(513,000)		(654,000)		(1,117,000)		(1,321,000)
Amortization of transition obligation	510,000		510,000		1,020,000		1,020,000
Amortization of prior service cost	(106,000)		(112,000)		(211,000)		(211,000)
Amortization of net loss	49,000		118,000		192,000		289,000
Net periodic benefit cost	984,000		976,000		2,097,000		2,156,000
Costs not recognized due to the effects of regulation	0	[1]	0	[1]	0	[1]	0	[1]
Net periodic benefit cost recognized for financial reporting	$ 984,000	[1]	$ 976,000	[1]	$ 2,097,000	[1]	$ 2,156,000	[1]

[1] Net periodic benefit costs for the pension plan are recognized for financial reporting based upon the authorization of each regulatory jurisdiction in which Idaho Power operates. Under IPUC order, income statement recognition of pension plan costs has been deferred until costs are recovered through rates.