Electric utility segment - Consolidating statement of income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating expenses
Purchased power	$ 161,000	$ 193,000	$ 446,000	$ 546,000
Total expenses	620,081	775,060	1,739,619	2,185,069
Operating income	97,095	92,036	239,331	264,433
Other income
Allowance for equity funds used during construction	2,057	1,937	5,366	4,933
Interest and other charges
Allowance for borrowed funds used during construction	737	740	1,918	1,877
Income taxes	29,516	27,264	70,406	76,302
Net income	51,144	48,279	118,974	136,293
Preferred stock dividends of subsidiaries	471	471	1,417	1,417
Net income for common stock	50,673	47,808	117,557	134,876
Hawaiian Electric Company
Condensed Income Statements, Captions [Line Items]
Revenues	463,394	579,777	1,254,142	1,623,223
Operating expenses
Fuel oil	142,194	229,068	364,875	628,164
Purchased power	119,302	142,121	329,922	406,895
Other operation and maintenance	69,621	71,584	206,133	199,091
Depreciation	29,389	27,302	88,167	81,903
Taxes, other than income taxes	43,923	54,412	119,603	152,545
Total expenses	404,429	524,487	1,108,700	1,468,598
Operating income	58,965	55,290	145,442	154,625
Other income
Allowance for equity funds used during construction	1,714	1,668	4,418	4,557
Equity in earnings of subsidiaries	11,858	9,800	29,174	28,576
Interest and other charges
Interest expense and other charges, net	(11,468)	(11,196)	(33,996)	(33,236)
Allowance for borrowed funds used during construction	605	634	1,557	1,728
Income before income taxes	61,674	56,196	146,595	156,250
Income taxes	18,398	17,047	43,064	46,911
Net income	43,276	39,149	103,531	109,339
Net income attributable to Hawaiian Electric	43,276	39,149	103,531	109,339
Preferred stock dividends of Hawaiian Electric	270	270	810	810
Net income for common stock	43,006	38,879	102,721	108,529
HELCO
Condensed Income Statements, Captions [Line Items]
Revenues	89,817	111,154	261,604	319,629
Operating expenses
Fuel oil	17,208	29,555	56,834	92,234
Purchased power	26,713	34,166	73,161	91,827
Other operation and maintenance	18,936	19,837	51,493	48,701
Depreciation	9,313	8,975	27,938	26,926
Taxes, other than income taxes	8,455	10,607	24,783	30,127
Total expenses	80,625	103,140	234,209	289,815
Operating income	9,192	8,014	27,395	29,814
Other income
Allowance for equity funds used during construction	148	142	458	328
Interest and other charges
Interest expense and other charges, net	(2,674)	(2,811)	(7,946)	(8,411)
Allowance for borrowed funds used during construction	53	54	164	126
Income before income taxes	6,719	5,399	20,071	21,857
Income taxes	2,397	1,965	7,210	8,149
Net income	4,322	3,434	12,861	13,708
Preferred stock dividends of subsidiaries	133	133	400	400
Net income attributable to Hawaiian Electric	4,189	3,301	12,461	13,308
Net income for common stock	4,189	3,301	12,461	13,308
Maui Electric
Condensed Income Statements, Captions [Line Items]
Revenues	94,941	112,656	264,057	319,265
Operating expenses
Fuel oil	36,231	50,809	96,961	145,591
Purchased power	14,503	16,595	42,726	47,399
Other operation and maintenance	15,096	16,892	48,893	47,691
Depreciation	5,654	5,317	16,735	15,961
Taxes, other than income taxes	8,932	10,169	25,054	30,111
Total expenses	80,416	99,782	230,369	286,753
Operating income	14,525	12,874	33,688	32,512
Other income
Allowance for equity funds used during construction	195	127	490	48
Interest and other charges
Interest expense and other charges, net	(2,440)	(2,429)	(7,299)	(7,403)
Allowance for borrowed funds used during construction	79	52	197	23
Income before income taxes	12,359	10,624	27,076	25,180
Income taxes	4,595	4,030	10,077	9,626
Net income	7,764	6,594	16,999	15,554
Preferred stock dividends of subsidiaries	95	95	286	286
Net income attributable to Hawaiian Electric	7,669	6,499	16,713	15,268
Net income for common stock	7,669	6,499	16,713	15,268
Other subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenues	0	0	0	0
Operating expenses
Other operation and maintenance	0	0	0	0
Total expenses	0	0	0	0
Operating income	0	0	0	0
Interest and other charges
Income before income taxes	0	0	0	0
Income taxes	0	0	0	0
Net income	0	0	0	0
Net income attributable to Hawaiian Electric	0	0	0	0
Net income for common stock	0	0	0	0
Consolidating adjustments
Condensed Income Statements, Captions [Line Items]
Revenues	(25)	(22)	(71)	(61)
Operating expenses
Operating income	(25)	(22)	(71)	(61)
Other income
Equity in earnings of subsidiaries	(11,858)	(9,800)	(29,174)	(28,576)
Interest and other charges
Interest expense and other charges, net	25	22	71	61
Income before income taxes	(11,858)	(9,800)	(29,174)	(28,576)
Income taxes	0	0	0	0
Net income	(11,858)	(9,800)	(29,174)	(28,576)
Net income attributable to Hawaiian Electric	(11,858)	(9,800)	(29,174)	(28,576)
Net income for common stock	(11,858)	(9,800)	(29,174)	(28,576)
HECO Consolidated
Condensed Income Statements, Captions [Line Items]
Revenues	648,127	803,565	1,779,732	2,262,056
Operating expenses
Fuel oil	195,633	309,432	518,670	865,989
Purchased power	160,518	192,882	445,809	546,121
Other operation and maintenance	103,653	108,313	306,519	295,483
Depreciation	44,356	41,594	132,840	124,790
Taxes, other than income taxes	61,310	75,188	169,440	212,783
Total expenses	565,470	727,409	1,573,278	2,045,166
Operating income	82,657	76,156	206,454	216,890
Other income
Allowance for equity funds used during construction	2,057	1,937	5,366	4,933
Interest and other charges
Interest expense and other charges, net	(16,557)	(16,414)	(49,170)	(48,989)
Allowance for borrowed funds used during construction	737	740	1,918	1,877
Income before income taxes	68,894	62,419	164,568	174,711
Income taxes	25,390	23,042	60,351	64,686
Net income	43,504	39,377	104,217	110,025
Preferred stock dividends of subsidiaries	228	228	686	686
Net income attributable to Hawaiian Electric	43,276	39,149	103,531	109,339
Preferred stock dividends of Hawaiian Electric	270	270	810	810
Net income for common stock	$ 43,006	$ 38,879	$ 102,721	$ 108,529