Electric utility segment - Consolidating Statement of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Expenses
Total expenses									$ 2,032,479	$ 2,280,429	$ 2,906,942
Operating income	$ 88,427	$ 105,442	$ 85,455	$ 68,851	$ 83,222	$ 97,095	$ 72,730	$ 69,506	348,175	322,553	332,600
Allowance for equity funds used during construction									8,325	6,928	6,771
Allowance for borrowed funds used during construction									(3,144)	(2,457)	(2,579)
Income before income taxes									373,841	254,788	265,598
Income taxes									123,695	93,021	95,579
Net income	45,107	127,613	44,601	32,825	42,793	51,144	35,491	32,339	250,146	161,767	170,019
Preferred stock dividends of subsidiaries									1,890	1,890	1,890
Net income for common stock	44,634	127,142	44,128	32,352	42,320	50,673	35,018	31,866	248,256	159,877	168,129
HECO
Revenues									1,474,384	1,644,181	2,142,245
Expenses
Fuel oil									305,359	458,069	821,246
Purchased power									431,009	440,983	537,821
Other operation and maintenance									273,176	284,583	283,532
Depreciation									126,086	117,682	109,204
Taxes, other than income taxes									141,615	156,871	201,426
Total expenses									1,277,245	1,458,188	1,953,229
Operating income									197,139	185,993	189,016
Allowance for equity funds used during construction									6,659	5,641	6,085
Equity in earnings of subsidiaries									42,391	42,920	40,964
Interest expense and other charges, net									(45,839)	(45,899)	(44,041)
Allowance for borrowed funds used during construction									(2,484)	(1,967)	(2,306)
Income before income taxes									202,834	190,622	194,330
Income taxes									59,437	53,828	55,609
Net income									143,397	136,794	138,721
Net income attributable to Hawaiian Electric									143,397	136,794	138,721
Preferred stock dividends of Hawaiian Electric									1,080	1,080	1,080
Net income for common stock									142,317	135,714	137,641
Hawaii Electric Light Company, Inc. (HELCO)
Revenues									311,385	345,549	422,200
Expenses
Fuel oil									55,094	71,851	117,215
Purchased power									81,018	97,503	123,226
Other operation and maintenance									63,897	63,098	65,471
Depreciation									37,797	37,250	35,904
Taxes, other than income taxes									29,017	32,312	39,521
Total expenses									266,823	302,014	381,337
Operating income									44,562	43,535	40,863
Allowance for equity funds used during construction									765	604	472
Interest expense and other charges, net									(11,555)	(10,773)	(11,030)
Allowance for borrowed funds used during construction									(294)	(215)	(182)
Income before income taxes									34,066	33,581	30,487
Income taxes									12,277	12,292	11,264
Net income									21,789	21,289	19,223
Preferred stock dividends of subsidiaries									534	534	534
Net income attributable to Hawaiian Electric									21,255	20,755	18,689
Net income for common stock									21,255	20,755	18,689
MECO
Revenues									308,705	345,517	422,965
Expenses
Fuel oil									94,251	124,680	193,224
Purchased power									50,713	55,610	60,961
Other operation and maintenance									68,460	65,408	61,609
Depreciation									23,178	22,448	21,279
Taxes, other than income taxes									29,230	32,702	39,916
Total expenses									265,832	300,848	376,989
Operating income									42,873	44,669	45,976
Allowance for equity funds used during construction									901	683	214
Interest expense and other charges, net									(9,536)	(9,779)	(9,773)
Allowance for borrowed funds used during construction									(366)	(275)	(91)
Income before income taxes									34,604	35,848	36,508
Income taxes									13,087	13,302	13,852
Net income									21,517	22,546	22,656
Preferred stock dividends of subsidiaries									381	381	381
Net income attributable to Hawaiian Electric									21,136	22,165	22,275
Net income for common stock									21,136	22,165	22,275
Consolidating adjustments
Revenues									(106)	(81)	(87)
Expenses
Operating income									(106)	(81)	(87)
Equity in earnings of subsidiaries									(42,391)	(42,920)	(40,964)
Interest expense and other charges, net									106	81	87
Income before income taxes									(42,391)	(42,920)	(40,964)
Income taxes									0
Net income									(42,391)	(42,920)	(40,964)
Net income attributable to Hawaiian Electric									(42,391)	(42,920)	(40,964)
Net income for common stock									(42,391)	(42,920)	(40,964)
HECO Consolidated
Revenues									2,094,368	2,335,166	2,987,323
Expenses
Fuel oil									454,704	654,600	1,131,685
Purchased power									562,740	594,096	722,008
Other operation and maintenance									405,533	413,089	410,612
Depreciation									187,061	177,380	166,387
Taxes, other than income taxes									199,862	221,885	280,863
Total expenses									1,809,900	2,061,050	2,711,555
Operating income	68,644	89,812	70,686	55,326	67,662	82,657	66,161	57,636	284,468	274,116	275,768
Allowance for equity funds used during construction									8,325	6,928	6,771
Interest expense and other charges, net									(66,824)	(66,370)	(64,757)
Allowance for borrowed funds used during construction									(3,144)	(2,457)	(2,579)
Income before income taxes									229,113	217,131	220,361
Income taxes									84,801	79,422	80,725
Net income	34,618	47,472	36,356	25,866	33,492	43,504	33,340	27,373	144,312	137,709	139,636
Preferred stock dividends of subsidiaries									915	915	915
Net income attributable to Hawaiian Electric									143,397	136,794	138,721
Preferred stock dividends of Hawaiian Electric									1,080	1,080	1,080
Net income for common stock	$ 34,119	$ 46,974	$ 35,857	$ 25,367	$ 32,993	$ 43,006	$ 32,841	$ 26,874	$ 142,317	$ 135,714	$ 137,641