REGULATORY MATTERS: Idaho Jurisdiction Power Cost Adjustment Mechanism (Details) - USD ($)	Jun. 01, 2015	Jun. 02, 2014	Jun. 01, 2014	Jun. 01, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2011
Idaho Power Cost Adjustment Mechanism [Line Items]
Regulatory Liabilities					$ 418,498,000	$ 401,607,000
Idaho Power Cost Adjustment
Idaho Power Cost Adjustment Mechanism [Line Items]
Percentage to be Shared with Customers					95.00%
Percentage to be Shared with Entity					5.00%
Percetange Sharing of Expenses Associated with PURPA Purchases					100.00%
Approved Rate Increase (Decrease), Amount	$ (11,600,000)	$ 106,000,000	$ (88,200,000)	$ 140,400,000
Regulatory Liabilities						$ 20,000,000	$ 27,100,000
IDAHO | Idaho Power Cost Adjustment
Idaho Power Cost Adjustment Mechanism [Line Items]
Approved Rate Increase (Decrease), Amount		$ 99,300,000