REGULATORY MATTERS: Level 4 (Details) - USD ($) $ in Thousands								3 Months Ended	9 Months Ended
	Jun. 01, 2016	Jun. 01, 2015	Jun. 01, 2014	Oct. 01, 2012	Jul. 01, 2012	Mar. 01, 2012	Jan. 01, 2012	Sep. 30, 2015	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014	Oct. 30, 2014
Rate Case
Additional accumulated deferred investment tax credit amortization									$ 1,500
Idaho Power Company
Rate Case
Additional accumulated deferred investment tax credit amortization									1,500
Idaho and Oregon General Rate Cases and Base Rate Adjustments | IDAHO
Rate Case
Authorized Rate of Return in Rate Case							7.86%
Total Retail Rate Base							$ 2,360,000
Approved Rate Increase (Decrease), Amount							$ 34,000
Idaho and Oregon General Rate Cases and Base Rate Adjustments | OREGON
Rate Case
Authorized Rate of Return in Rate Case						7.757%
Approved Rate Increase (Decrease), Amount						$ 1,800
Public Utilities, Approved Return on Equity, Percentage						9.90%
Cost Recovery for Langley Gulch Power Plant | IDAHO
Rate Case
Approved Rate Increase (Decrease), Amount					$ 58,100
Increase (Decrease) in Rate Base					$ 335,900
Cost Recovery for Langley Gulch Power Plant | OREGON
Rate Case
Approved Rate Increase (Decrease), Amount				$ 3,000
Idaho Settlement Stipulation - Investment Tax Credits and Sharing Mechanism
Rate Case
Authorized Return on Equity in Rate Case, Minimum												9.50%
Authorized Return on Equity in Rate Case, Mid-point												10.00%
Authorized Return on Equity in Rate Case, Maximum												10.50%
Investment Tax Credits Maximum In One Year In Rate Case												$ 25,000
Investment Tax Credits, Maximum, in Rate Case									43,500			$ 45,000
Additional accumulated deferred investment tax credit amortization									$ 1,500
Percentage to be Shared with Customers												75.00%
Percentage to be Shared with Entity												25.00%
Percent To Be Shared With Customers, Power Cost Adjustment												50.00%
Percent To Be Shared With Customers, Pension Balancing												25.00%
Regulatory Liabilities										$ 3,200	$ 8,000
Annual Power Cost Adjustment Mechanism Filing [Member]
Rate Case
Approved Rate Increase (Decrease), Amount	$ 17,300	$ (11,600)	$ 106,000					$ (1,500)
Regulatory Liabilities										$ 4,000	$ 4,000
Annual Power Cost Adjustment Mechanism Filing [Member] | IDAHO
Rate Case
Approved Rate Increase (Decrease), Amount			99,000
Idaho Fixed Cost Adjustment Mechanism Annual Filing
Rate Case
Approved Rate Increase (Decrease), Amount	11,200	2,000
Annual fixed cost adjustment mechanism deferral	$ 28,100	$ 16,900	$ 14,900