Electric utility segment - Condensed consolidating statement of income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Condensed Income Statements, Captions [Line Items]
Revenues	$ 632,281	$ 566,244	$ 1,223,843	$ 1,117,204
Expenses
Purchased power	153,000	139,000	280,000	255,000
Total expenses	556,385	480,789	1,080,085	962,898
Total operating income	75,896	85,455	143,758	154,306
Allowance for equity funds used during construction	3,027	1,997	5,426	3,736
Allowance for borrowed funds used during construction	1,143	760	2,032	1,422
Income before income taxes	59,626	70,911	111,208	122,037
Income taxes	20,492	26,310	37,408	44,611
Net income	39,134	44,601	73,800	77,426
Preferred stock dividends of subsidiaries	473	473	946	946
Net income for common stock	38,661	44,128	72,854	76,480
Hawaiian Electric Company
Condensed Income Statements, Captions [Line Items]
Revenues	394,414	347,010	757,257	684,185
Expenses
Fuel oil	99,814	62,234	197,815	136,319
Purchased power	116,458	103,062	216,605	194,979
Other operation and maintenance	70,961	68,197	138,239	137,755
Depreciation	32,723	31,522	65,445	63,044
Taxes, other than income taxes	37,619	33,414	72,659	66,098
Total expenses	357,575	298,429	690,763	598,195
Total operating income	36,839	48,581	66,494	85,990
Allowance for equity funds used during construction	2,659	1,559	4,715	2,965
Equity in earnings of subsidiaries	7,936	10,883	16,539	18,812
Interest expense and other charges, net	(12,562)	(10,345)	(24,619)	(22,210)
Allowance for borrowed funds used during construction	988	587	1,737	1,116
Income before income taxes	35,860	51,265	64,866	86,673
Income taxes	9,946	15,138	17,217	24,909
Net income	25,914	36,127	47,649	61,764
Preferred stock dividends of subsidiaries	0	0	0	0
Net income attributable to Hawaiian Electric	25,914	36,127	47,649	61,764
Preferred stock dividends of Hawaiian Electric	270	270	540	540
Net income for common stock	25,644	35,857	47,109	61,224
HELCO
Condensed Income Statements, Captions [Line Items]
Revenues	81,710	73,652	160,692	146,835
Expenses
Fuel oil	14,475	11,748	31,732	26,122
Purchased power	23,482	19,360	42,071	36,157
Other operation and maintenance	17,558	15,116	33,074	31,557
Depreciation	9,686	9,449	19,371	18,898
Taxes, other than income taxes	7,702	6,905	15,152	13,796
Total expenses	72,903	62,578	141,400	126,530
Total operating income	8,807	11,074	19,292	20,305
Allowance for equity funds used during construction	134	206	249	333
Equity in earnings of subsidiaries	0	0	0	0
Interest expense and other charges, net	(2,996)	(2,669)	(6,000)	(5,634)
Allowance for borrowed funds used during construction	55	79	100	128
Income before income taxes	6,000	8,690	13,641	15,132
Income taxes	2,235	3,337	5,158	5,683
Net income	3,765	5,353	8,483	9,449
Preferred stock dividends of subsidiaries	133	133	267	267
Net income attributable to Hawaiian Electric	3,632	5,220	8,216	9,182
Preferred stock dividends of Hawaiian Electric	0	0	0	0
Net income for common stock	3,632	5,220	8,216	9,182
Maui Electric
Condensed Income Statements, Captions [Line Items]
Revenues	80,765	74,758	157,558	146,464
Expenses
Fuel oil	26,970	17,917	55,982	43,198
Purchased power	13,127	16,636	21,515	23,781
Other operation and maintenance	17,855	16,250	35,301	34,159
Depreciation	5,747	5,789	11,556	11,599
Taxes, other than income taxes	7,651	7,110	14,984	13,973
Total expenses	71,350	63,702	139,338	126,710
Total operating income	9,415	11,056	18,220	19,754
Allowance for equity funds used during construction	234	232	462	438
Equity in earnings of subsidiaries	0	0	0	0
Interest expense and other charges, net	(2,670)	(2,114)	(5,120)	(4,604)
Allowance for borrowed funds used during construction	100	94	195	178
Income before income taxes	7,079	9,268	13,757	15,766
Income taxes	2,679	3,509	5,243	5,945
Net income	4,400	5,759	8,514	9,821
Preferred stock dividends of subsidiaries	96	96	191	191
Net income attributable to Hawaiian Electric	4,304	5,663	8,323	9,630
Preferred stock dividends of Hawaiian Electric	0	0	0	0
Net income for common stock	4,304	5,663	8,323	9,630
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	(14)	(25)	(21)	(37)
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	(14)	(25)	(21)	(37)
Allowance for equity funds used during construction	0	0	0	0
Equity in earnings of subsidiaries	(7,936)	(10,883)	(16,539)	(18,812)
Interest expense and other charges, net	14	25	21	37
Allowance for borrowed funds used during construction	0	0	0	0
Income before income taxes	(7,936)	(10,883)	(16,539)	(18,812)
Income taxes	0	0	0	0
Net income	(7,936)	(10,883)	(16,539)	(18,812)
Preferred stock dividends of subsidiaries	0	0	0	0
Net income attributable to Hawaiian Electric	(7,936)	(10,883)	(16,539)	(18,812)
Preferred stock dividends of Hawaiian Electric	0	0	0	0
Net income for common stock	(7,936)	(10,883)	(16,539)	(18,812)
Hawaiian Electric Company, Inc. and Subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenues	556,875	495,395	1,075,486	977,447
Expenses
Fuel oil	141,259	91,899	285,529	205,639
Purchased power	153,067	139,058	280,191	254,917
Other operation and maintenance	106,374	99,563	206,614	203,471
Depreciation	48,156	46,760	96,372	93,541
Taxes, other than income taxes	52,972	47,429	102,795	93,867
Total expenses	501,828	424,709	971,501	851,435
Total operating income	55,047	70,686	103,985	126,012
Allowance for equity funds used during construction	3,027	1,997	5,426	3,736
Equity in earnings of subsidiaries	0	0	0	0
Interest expense and other charges, net	(18,214)	(15,103)	(35,718)	(32,411)
Allowance for borrowed funds used during construction	1,143	760	2,032	1,422
Income before income taxes	41,003	58,340	75,725	98,759
Income taxes	14,860	21,984	27,618	36,537
Net income	26,143	36,356	48,107	62,222
Preferred stock dividends of subsidiaries	229	229	458	458
Net income attributable to Hawaiian Electric	25,914	36,127	47,649	61,764
Preferred stock dividends of Hawaiian Electric	270	270	540	540
Net income for common stock	$ 25,644	$ 35,857	$ 47,109	$ 61,224