INCOME TAXES: Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Regulatory liabilities	$ 96,599	$ 98,042
Deferred compensation	21,946	21,871
Deferred revenue	39,039	35,137
Tax credits	76,125	100,041
Partnership investments	7,911	4,200
Retirement benefits	114,124	91,867
Other	11,347	9,299
Total	367,091	360,457
Deferred tax liabilities:
Property, plant and equipment	286,583	294,471
Regulatory assets	646,886	614,144
Partnership investments	3,565	3,875
Retirement benefits	132,764	108,440
Other	43,524	39,405
Total	1,113,322	1,060,335
Net deferred tax liabilities	746,231	699,878
Idaho Power Company
Deferred tax assets:
Regulatory liabilities	96,599	98,042
Deferred compensation	21,946	21,826
Deferred revenue	39,039	35,137
Tax credits	24,489	44,532
Partnership investments	4,912	1,086
Retirement benefits	114,124	91,867
Other	11,107	9,121
Total	312,216	301,611
Deferred tax liabilities:
Property, plant and equipment	286,583	294,471
Regulatory assets	646,886	614,144
Partnership investments	0	0
Retirement benefits	132,764	108,440
Other	40,385	37,795
Total	1,106,618	1,054,850
Net deferred tax liabilities	$ 794,402	$ 753,239