Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities:
Net Income	$ 194,475	$ 193,754	$ 182,294
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	142,581	137,088	133,776
Deferred income taxes and investment tax credits	38,645	19,163	65,568
Changes in regulatory assets and liabilities	13,699	32,135	(25,581)
Pension and postretirement benefit plan expense	30,207	44,627	45,907
Contributions to pension and postretirement benefit plans	(42,843)	(33,720)	(33,393)
Earnings of unconsolidated equity-method investments	(11,128)	(12,372)	(11,939)
Distributions from unconsolidated equity-method investments	12,458	5,261	17,526
Allowance for equity funds used during construction	(21,785)	(17,931)	(14,858)
Gain on sale of investments and assets	(97)	(193)	(11,678)
Other non-cash adjustments to net income, net	2,788	5,085	3,297
Change in:
Accounts receivable	4,740	20,433	(29,557)
Accounts payable and other accrued liabilities	2,440	6,359	(517)
Taxes accrued/receivable	818	(13,631)	4,747
Other current assets	(14,861)	(13,124)	(12,165)
Other current liabilities	403	1,771	1,819
Other assets	3,021	(3,655)	(830)
Other liabilities	(2,367)	(6,707)	(8,867)
Net cash provided by operating activities	353,194	364,343	305,549
Investing Activities:
Additions to property, plant and equipment	(294,021)	(274,094)	(246,674)
Payments received from transmission project joint funding partners	11,377	0	11,364
Purchase of available-for-sale securities	(14,106)	(8,000)	(32,661)
Proceeds from sale of available-for-sale securities	34,243	0	25,661
Purchase of life insurance investment	(30,000)	0	0
Other	801	9,674	5,717
Net cash used in investing activities	(291,706)	(272,420)	(236,593)
Financing Activities:
Issuance of long-term debt	250,000	0	150,000
Retirement of long-term debt	(121,064)	(1,064)	(71,064)
Dividends on common stock	(96,810)	(88,489)	(78,832)
Net change in short-term borrowings	(11,300)	(23,450)	(14,950)
Issuance of common stock	0	195	255
Acquisition of treasury stock	(3,277)	(2,737)	(2,124)
Make-whole premium on retirement of long-term debt	(17,872)	0	0
Other	(3,171)	2,268	(606)
Net cash used in financing activities	(3,494)	(113,277)	(17,321)
Net increase (decrease) in cash and cash equivalents	57,994	(21,354)	51,635
Cash and cash equivalents at beginning of the year	56,808	78,162	26,527
Cash and cash equivalents at end of the year	114,802	56,808	78,162
Cash paid during the period for:
Income taxes	8,857	11,364	1,437
Interest (net of amount capitalized)	79,442	77,295	77,968
Non-cash investing activities:
Additions to property, plant and equipment in accounts payable	23,840	28,438	24,246
Idaho Power Company
Operating Activities:
Net Income	190,983	189,387	176,741
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	141,972	136,496	133,135
Deferred income taxes and investment tax credits	25,702	15,454	59,355
Changes in regulatory assets and liabilities	13,699	32,135	(25,581)
Pension and postretirement benefit plan expense	30,185	44,579	45,861
Contributions to pension and postretirement benefit plans	(42,821)	(33,672)	(33,347)
Earnings of unconsolidated equity-method investments	(9,773)	(10,814)	(10,242)
Distributions from unconsolidated equity-method investments	10,833	3,586	14,901
Allowance for equity funds used during construction	(21,785)	(17,931)	(14,858)
Gain on sale of investments and assets	(97)	(186)	(11,678)
Other non-cash adjustments to net income, net	(687)	2,087	629
Change in:
Accounts receivable	1,998	20,072	(31,472)
Accounts payable and other accrued liabilities	2,646	6,183	(397)
Taxes accrued/receivable	17,179	(22,911)	6,740
Other current assets	(14,849)	(13,137)	(12,166)
Other current liabilities	443	1,776	1,721
Other assets	3,021	(3,655)	(831)
Other liabilities	(2,222)	(6,238)	(8,603)
Net cash provided by operating activities	346,427	343,211	289,908
Investing Activities:
Additions to property, plant and equipment	(293,968)	(273,911)	(246,670)
Payments received from transmission project joint funding partners	11,377	0	11,364
Purchase of available-for-sale securities	(14,106)	(8,000)	(32,661)
Proceeds from sale of available-for-sale securities	34,243	0	25,661
Purchase of life insurance investment	(30,000)	0	0
Other	706	8,508	3,971
Net cash used in investing activities	(291,748)	(273,403)	(238,335)
Financing Activities:
Issuance of long-term debt	250,000	0	150,000
Retirement of long-term debt	(121,064)	(1,064)	(71,064)
Dividends on common stock	(96,907)	(88,584)	(78,926)
Make-whole premium on retirement of long-term debt	(17,872)	0	0
Other	(4,775)	0	(2,299)
Net cash used in financing activities	9,382	(89,648)	(2,289)
Net increase (decrease) in cash and cash equivalents	64,061	(19,840)	49,284
Cash and cash equivalents at beginning of the year	46,695	66,535	17,251
Cash and cash equivalents at end of the year	110,756	46,695	66,535
Cash paid during the period for:
Income taxes	7,487	26,116	9,667
Interest (net of amount capitalized)	79,226	77,063	77,583
Non-cash investing activities:
Additions to property, plant and equipment in accounts payable	$ 23,840	$ 28,438	$ 24,246