LONG-TERM DEBT: Long-term debt narrative Level 4 (Details) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Mar. 31, 2018	May 19, 2016
Debt Instrument [Line Items]
Make-Whole Premium			$ 0	$ 4,607	$ 0
Repayments of Debt			166,100	130,000	1,064
First Mortgage Bonds 4.20 K Series due 2048
Debt Instrument [Line Items]
First mortgage bonds			$ 220,000	$ 220,000			$ 220,000
Debt Instrument, Interest Rate, Stated Percentage			4.20%	4.20%			4.20%
First mortgage bonds 4.20% Series due 2046
Debt Instrument [Line Items]
First mortgage bonds			$ 120,000	$ 120,000
Debt Instrument, Interest Rate, Stated Percentage			4.05%	4.05%
Pollution Control Bonds 5.15 due 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[1]		1.45%	5.15%
Pollution Control Bond 5.25 due 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[1]		1.70%	5.25%
Idaho Power Company
Debt Instrument [Line Items]
Make-Whole Premium			$ 0	$ 4,607	0
Debt Instrument, Interest Rate, Effective Percentage			4.50%	4.83%
Repayments of Debt			$ 166,100	$ 130,000	$ 1,064
Principal amount of debt securities and first mortgage bonds authorized			$ 500,000
Extension Period of State Regulatory Authorization to Issue Debt			2 years
Debt instrument interest rate limit			7.00%
Indenture, Unused Borrowing Capacity, Amount			$ 1,900,000
Percent of Operating Revenues Required to be Spent or Appropriated			15.00%
Time Period Expenditures or Appropriations can be Made Up			5 years
Bonds issuable maximum amount ending			$ 2,500,000					$ 2,000,000
Earnings test does not apply to refunding bonds that mature in less than this period of time			2 years
Indenture, Unused Borrowing Capacity available			$ 669,000
Idaho Power Company | First mortgage bonds 4.50 Series due 2020
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.50%
Repayments of Debt		$ 130,000
Idaho Power Company | Pollution Control Bonds 5.15 due 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						5.15%
Repayments of Debt			$ 49,800
Idaho Power Company | Humboldt County Pollution Control Revenue Bonds [Domain]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			1.45%
Idaho Power Company | Pollution Control Bond 5.25 due 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						5.25%
Repayments of Debt			$ 116,300
Idaho Power Company | Sweetwater County Pollution Control Revenue Bond due 2026 1.7 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			1.70%

[1] Humboldt County and Sweetwater County Pollution Control Revenue Bonds are secured by the first mortgage, bringing the total first mortgage bonds outstanding at December 31, 2019, to $1.831 billion. These two bonds were purchased and remarketed in August of 2019. See "Long-Term Debt Issuances, Maturities, and Redemptions" below.