INCOME TAXES: Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Regulatory liabilities	$ 51,131	$ 55,490
Deferred compensation	27,573	25,355
Deferred revenue	34,282	28,529
Tax credits	147,299	154,044
Partnership investments	7,220	8,190
Retirement benefits	126,885	132,571
Other	11,245	15,222
Total	405,635	419,401
Deferred tax liabilities:
Property, plant and equipment	474,879	451,118
Regulatory assets	875,028	802,188
Power cost adjustments	18,489	23,192
Partnership investments	16,925	17,492
Retirement benefits	126,090	122,360
Other	31,600	25,982
Total	1,543,011	1,442,332
Net deferred tax liabilities	1,137,376	1,022,931
Idaho Power Company
Deferred tax assets:
Regulatory liabilities	51,131	55,490
Deferred compensation	27,489	25,240
Deferred revenue	34,282	28,529
Tax credits	30,307	26,843
Retirement benefits	126,885	132,571
Other	10,745	14,553
Total	280,839	283,226
Deferred tax liabilities:
Property, plant and equipment	474,879	451,118
Regulatory assets	875,028	802,188
Power cost adjustments	18,489	23,192
Partnership investments	9,829	10,227
Retirement benefits	126,090	122,360
Other	28,895	22,252
Total	1,533,210	1,431,337
Net deferred tax liabilities	$ 1,252,371	$ 1,148,111