COMMITMENTS: Commitments Level 4 (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) MWh	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2022 MWh
Bridger Coal Company
Long-term Purchase Commitment
IERCo guarantee of BCC reclamation obligation	$ 175,000
Distributions from Reclamation Trust Fund	0
Guarantor Obligations Total Reclamation Trust Fund	$ 139,500
Idaho Power Company
Long-term Purchase Commitment
Range of contract length, mimimum	1 year
Range of contract length, maximum	35 years
Utilities Operating Expense, Purchased Power under Long-term Contracts	$ 187,000	$ 190,000	$ 170,000
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	33.00%
IERCo guarantee of BCC reclamation obligation	$ 58,300
Idaho Power Company | Joint-operating agreement payment [Member]
Long-term Purchase Commitment
Purchase Obligation Estimated Due Current	2,678
Purchase Obligation Estimated Future Payments Due In Two Years	2,678
Purchase Obligation Estimated Future Payments Due In Three Years	2,678
Purchase Obligation Estimated Future Payments Due In Four Years	2,678
Purchase Obligation Estimated Future Payments Due In Five Years	2,678
Purchase Obligation Estimated Future Payments Due In Six Years And Thereafter	13,391
Idaho Power Company | Easements and Other payments [Member]
Long-term Purchase Commitment
Purchase Obligation Estimated Due Current	269
Purchase Obligation Estimated Future Payments Due In Two Years	1,124
Purchase Obligation Estimated Future Payments Due In Three Years	1,072
Purchase Obligation Estimated Future Payments Due In Four Years	1,062
Purchase Obligation Estimated Future Payments Due In Five Years	1,055
Purchase Obligation Estimated Future Payments Due In Six Years And Thereafter	16,408
Idaho Power Company | Other operations and maintenance
Long-term Purchase Commitment
Purchase Obligation Estimated Due Current	47,547
Purchase Obligation Estimated Future Payments Due In Two Years	13,797
Purchase Obligation Estimated Future Payments Due In Three Years	16,468
Purchase Obligation Estimated Future Payments Due In Four Years	7,143
Purchase Obligation Estimated Future Payments Due In Five Years	7,354
Purchase Obligation Estimated Future Payments Due In Six Years And Thereafter	55,768
Idaho Power Company | FERC and other industry-related fees
Long-term Purchase Commitment
Purchase Obligation Estimated Due Current	14,178
Purchase Obligation Estimated Future Payments Due In Two Years	13,874
Purchase Obligation Estimated Future Payments Due In Three Years	13,056
Purchase Obligation Estimated Future Payments Due In Four Years	13,056
Purchase Obligation Estimated Future Payments Due In Five Years	13,056
Purchase Obligation Estimated Future Payments Due In Six Years And Thereafter	$ 65,278
Idaho Power Company | CSPP on-line [Member]
Long-term Purchase Commitment
Nameplate Capacity (in MW) | MWh	1,136
Idaho Power Company | Cogeneration and power production
Long-term Purchase Commitment
Purchase Obligation Estimated Due Current	$ 241,835
Purchase Obligation Estimated Future Payments Due In Two Years	248,481
Purchase Obligation Estimated Future Payments Due In Three Years	251,964
Purchase Obligation Estimated Future Payments Due In Four Years	262,735
Purchase Obligation Estimated Future Payments Due In Five Years	266,061
Purchase Obligation Estimated Future Payments Due In Six Years And Thereafter	2,739,123
Idaho Power Company | Fuel purchase commitments
Long-term Purchase Commitment
Purchase Obligation Estimated Due Current	55,693
Purchase Obligation Estimated Future Payments Due In Two Years	36,069
Purchase Obligation Estimated Future Payments Due In Three Years	8,389
Purchase Obligation Estimated Future Payments Due In Four Years	8,379
Purchase Obligation Estimated Future Payments Due In Five Years	8,371
Purchase Obligation Estimated Future Payments Due In Six Years And Thereafter	75,074
Forecast [Member] | Capacity [Member] | Idaho Power Company | CSPP not on-line [Member]
Long-term Purchase Commitment
Nameplate Capacity (in MW) | MWh				11
Contracts with no expiration [Member] | Idaho Power Company | Joint-operating agreement payment [Member]
Long-term Purchase Commitment
Purchase Obligation	27,000
Contracts with no expiration [Member] | Idaho Power Company | Other operations and maintenance
Long-term Purchase Commitment
Purchase Obligation	48,000
Contracts with no expiration [Member] | Idaho Power Company | FERC and other industry-related fees
Long-term Purchase Commitment
Purchase Obligation	$ 131,000