INVESTMENTS: Investments Level 4 (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of investments in debt and equity securities
Equity method investment	$ 11,102	$ 11,366
Investments in affordable housing	3,665	3,446
Total investments	98,218	101,178
Earnings of unconsolidated equity-method investments	12,370	12,449	$ 11,374
Idaho Power Company
Summary of investments in debt and equity securities
Equity method investment	40,713	49,878
Exchange traded short-term bond funds and cash equivalents	42,648	36,471
Executive Deferred Compensation Plan Assets	90	17
Total investments	$ 83,451	86,366
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	33.00%
Earnings of unconsolidated equity-method investments	$ 10,285	10,712	9,267
Proceeds from sales	5,080	5,007	4,989
Gross realized gains from sales	0	0	0
Bridger Coal Company
Summary of investments in debt and equity securities
Earnings of unconsolidated equity-method investments	$ 10,285	10,712	9,267
Ida-West Energy
Summary of investments in debt and equity securities
Jointly Owned Utility Plant, Proportionate Ownership Share	50.00%
Earnings of unconsolidated equity-method investments	$ 2,085	$ 1,737	$ 2,107

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