Electric utility segment - Condensed consolidating statement of income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Income Statements, Captions [Line Items]
Revenues	$ 673,185	$ 646,055	$ 1,897,028	$ 1,763,259
Expenses
Purchased power	161,000	158,000	441,000	413,000
Total expenses	563,640	540,613	1,643,725	1,503,511
Total operating income	109,545	105,442	253,303	259,748
Allowance for equity funds used during construction	3,482	2,274	8,908	6,010
Allowance for borrowed funds used during construction	1,339	854	3,371	2,276
Income before income taxes	95,139	179,205	206,347	301,242
Income taxes	34,595	51,592	72,003	96,203
Net income	60,544	127,613	134,344	205,039
Preferred stock dividends of subsidiaries	471	471	1,417	1,417
Net income for common stock	60,073	127,142	132,927	203,622
Hawaiian Electric Company
Condensed Income Statements, Captions [Line Items]
Revenues	429,267	404,352	1,186,524	1,088,537
Expenses
Fuel oil	103,959	88,676	301,774	224,995
Purchased power	123,893	118,751	340,498	313,730
Other operation and maintenance	66,221	64,683	204,460	202,438
Depreciation	32,722	31,520	98,167	94,564
Taxes, other than income taxes	40,824	38,666	113,483	104,764
Total expenses	367,619	342,296	1,058,382	940,491
Total operating income	61,648	62,056	128,142	148,046
Allowance for equity funds used during construction	3,108	1,806	7,823	4,771
Equity in earnings of subsidiaries	12,767	14,729	29,306	33,541
Interest expense and other charges, net	(11,786)	(11,903)	(36,405)	(34,113)
Allowance for borrowed funds used during construction	1,173	669	2,910	1,785
Income before income taxes	66,910	67,357	131,776	154,030
Income taxes	19,153	20,113	36,370	45,022
Net income	47,757	47,244	95,406	109,008
Preferred stock dividends of subsidiaries	0	0	0	0
Net income attributable to Hawaiian Electric	47,757	47,244	95,406	109,008
Preferred stock dividends of Hawaiian Electric	270	270	810	810
Net income for common stock	47,487	46,974	94,596	108,198
HELCO
Condensed Income Statements, Captions [Line Items]
Revenues	84,334	83,105	245,026	229,940
Expenses
Fuel oil	15,754	14,603	47,486	40,725
Purchased power	21,332	22,728	63,403	58,885
Other operation and maintenance	16,593	15,017	49,667	46,574
Depreciation	9,685	9,449	29,056	28,347
Taxes, other than income taxes	7,928	7,836	23,080	21,632
Total expenses	71,292	69,633	212,692	196,163
Total operating income	13,042	13,472	32,334	33,777
Allowance for equity funds used during construction	167	238	416	571
Equity in earnings of subsidiaries	0	0	0	0
Interest expense and other charges, net	(2,899)	(2,972)	(8,899)	(8,606)
Allowance for borrowed funds used during construction	72	91	172	219
Income before income taxes	10,382	10,829	24,023	25,961
Income taxes	3,815	3,392	8,973	9,075
Net income	6,567	7,437	15,050	16,886
Preferred stock dividends of subsidiaries	133	133	400	400
Net income attributable to Hawaiian Electric	6,434	7,304	14,650	16,486
Preferred stock dividends of Hawaiian Electric	0	0	0	0
Net income for common stock	6,434	7,304	14,650	16,486
Maui Electric
Condensed Income Statements, Captions [Line Items]
Revenues	85,198	84,831	242,756	231,295
Expenses
Fuel oil	26,545	25,345	82,527	68,543
Purchased power	15,122	16,271	36,637	40,052
Other operation and maintenance	17,288	15,089	52,589	49,248
Depreciation	5,799	5,790	17,355	17,389
Taxes, other than income taxes	8,028	8,017	23,012	21,990
Total expenses	72,782	70,512	212,120	197,222
Total operating income	12,416	14,319	30,636	34,073
Allowance for equity funds used during construction	207	230	669	668
Equity in earnings of subsidiaries	0	0	0	0
Interest expense and other charges, net	(2,252)	(2,483)	(7,372)	(7,087)
Allowance for borrowed funds used during construction	94	94	289	272
Income before income taxes	10,465	12,160	24,222	27,926
Income taxes	4,037	4,640	9,280	10,585
Net income	6,428	7,520	14,942	17,341
Preferred stock dividends of subsidiaries	95	95	286	286
Net income attributable to Hawaiian Electric	6,333	7,425	14,656	17,055
Preferred stock dividends of Hawaiian Electric	0	0	0	0
Net income for common stock	6,333	7,425	14,656	17,055
Other subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenues	0	0	0	0
Expenses
Fuel oil	0	0	0	0
Purchased power	0	0	0	0
Other operation and maintenance	0	0	0	0
Depreciation	0	0	0	0
Taxes, other than income taxes	0	0	0	0
Total expenses	0	0	0	0
Total operating income	0	0	0	0
Allowance for equity funds used during construction	0	0	0	0
Equity in earnings of subsidiaries	0	0	0	0
Interest expense and other charges, net	0	0	0	0
Allowance for borrowed funds used during construction	0	0	0	0
Income before income taxes	0	0	0	0
Income taxes	0	0	0	0
Net income	0	0	0	0
Preferred stock dividends of subsidiaries	0	0	0	0
Net income attributable to Hawaiian Electric	0	0	0	0
Preferred stock dividends of Hawaiian Electric	0	0	0	0
Net income for common stock	0	0	0	0
Consolidating adjustments
Condensed Income Statements, Captions [Line Items]
Revenues	(30)	(35)	(51)	(72)
Expenses
Fuel oil	0	0	0	0
Purchased power	0	0	0	0
Other operation and maintenance	0	0	0	0
Depreciation	0	0	0	0
Taxes, other than income taxes	0	0	0	0
Total expenses	0	0	0	0
Total operating income	(30)	(35)	(51)	(72)
Allowance for equity funds used during construction	0	0	0	0
Equity in earnings of subsidiaries	(12,767)	(14,729)	(29,306)	(33,541)
Interest expense and other charges, net	30	35	51	72
Allowance for borrowed funds used during construction	0	0	0	0
Income before income taxes	(12,767)	(14,729)	(29,306)	(33,541)
Income taxes	0	0	0	0
Net income	(12,767)	(14,729)	(29,306)	(33,541)
Preferred stock dividends of subsidiaries	0	0	0	0
Net income attributable to Hawaiian Electric	(12,767)	(14,729)	(29,306)	(33,541)
Preferred stock dividends of Hawaiian Electric	0	0	0	0
Net income for common stock	(12,767)	(14,729)	(29,306)	(33,541)
Hawaiian Electric Company, Inc. and Subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenues	598,769	572,253	1,674,255	1,549,700
Expenses
Fuel oil	146,258	128,624	431,787	334,263
Purchased power	160,347	157,750	440,538	412,667
Other operation and maintenance	100,102	94,789	306,716	298,260
Depreciation	48,206	46,759	144,578	140,300
Taxes, other than income taxes	56,780	54,519	159,575	148,386
Total expenses	511,693	482,441	1,483,194	1,333,876
Total operating income	87,076	89,812	191,061	215,824
Allowance for equity funds used during construction	3,482	2,274	8,908	6,010
Equity in earnings of subsidiaries	0	0	0	0
Interest expense and other charges, net	(16,907)	(17,323)	(52,625)	(49,734)
Allowance for borrowed funds used during construction	1,339	854	3,371	2,276
Income before income taxes	74,990	75,617	150,715	174,376
Income taxes	27,005	28,145	54,623	64,682
Net income	47,985	47,472	96,092	109,694
Preferred stock dividends of subsidiaries	228	228	686	686
Net income attributable to Hawaiian Electric	47,757	47,244	95,406	109,008
Preferred stock dividends of Hawaiian Electric	270	270	810	810
Net income for common stock	$ 47,487	$ 46,974	$ 94,596	$ 108,198