Electric utility segment - Condensed consolidating balance sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Utility property, plant and equipment
Total property, plant and equipment, net	$ 4,726,524	$ 4,603,465
Current assets
Cash and cash equivalents	210,381	278,452	$ 257,208	$ 300,478
Other long-term assets
Total assets	12,693,805	12,425,506
Capitalization
Common stock equity	2,075,029	2,066,753	1,966,182	1,927,640
Cumulative preferred stock—not subject to mandatory redemption	0	0
Current liabilities
Interest and preferred dividends payable	22,124	25,225
Deferred credits and other liabilities
Deferred income taxes	750,413	728,806
Contributions in aid of construction	543,204	543,525
Total liabilities and shareholders’ equity	12,693,805	12,425,506
Hawaiian Electric Company
Utility property, plant and equipment
Land	43,971	43,956
Plant and equipment	4,318,460	4,241,060
Less accumulated depreciation	(1,423,042)	(1,382,972)
Construction in progress	232,965	180,194
Utility property, plant and equipment, net	3,172,354	3,082,238
Nonutility property, plant and equipment, less accumulated depreciation	5,763	5,760
Total property, plant and equipment, net	3,178,117	3,087,998
Investment in wholly owned subsidiaries, at equity	553,764	550,946
Current assets
Cash and cash equivalents	29,988	61,388	19,842	16,281
Advances to affiliates	0	0
Customer accounts receivable, net	88,614	86,373
Accrued unbilled revenues, net	74,640	65,821
Other accounts receivable, net	9,707	7,652
Fuel oil stock, at average cost	51,489	47,239
Materials and supplies, at average cost	30,716	29,928
Prepayments and other	25,695	16,502
Regulatory assets	65,891	60,185
Total current assets	376,740	375,088
Other long-term assets
Regulatory assets	638,480	662,232
Unamortized debt expense	497	151
Other	48,164	43,743
Other	687,141	706,126
Total assets	4,795,762	4,720,158
Capitalization
Common stock equity	1,803,506	1,799,787	1,743,006	1,728,325
Cumulative preferred stock—not subject to mandatory redemption	22,293	22,293
Long-term debt, net	915,208	915,437
Total capitalization	2,741,007	2,737,517
Current liabilities
Short-term borrowings from non-affiliates	43,990
Short-term borrowings from affiliate	5,100	13,500
Accounts payable	123,986	86,369
Interest and preferred dividends payable	13,584	15,761
Taxes accrued	98,156	120,176
Regulatory liabilities	126	0
Other	38,964	41,352
Total current liabilities	323,906	277,158
Deferred credits and other liabilities
Deferred income taxes	542,109	524,433
Regulatory liabilities	297,006	281,112
Unamortized tax credits	59,537	57,844
Defined benefit pension and other postretirement benefit plans liability	435,614	444,458
Other	49,798	49,191
Total deferred credits and other liabilities	1,384,064	1,357,038
Contributions in aid of construction	346,785	348,445
Total liabilities and shareholders’ equity	4,795,762	4,720,158
HELCO
Utility property, plant and equipment
Land	6,191	6,181
Plant and equipment	1,267,529	1,255,185
Less accumulated depreciation	(518,266)	(507,666)
Construction in progress	16,734	12,510
Utility property, plant and equipment, net	772,188	766,210
Nonutility property, plant and equipment, less accumulated depreciation	115	115
Total property, plant and equipment, net	772,303	766,325
Investment in wholly owned subsidiaries, at equity	0	0
Current assets
Cash and cash equivalents	7,104	10,749	5,264	2,682
Advances to affiliates	4,100	3,500
Customer accounts receivable, net	18,847	20,055
Accrued unbilled revenues, net	14,166	13,564
Other accounts receivable, net	2,471	2,445
Fuel oil stock, at average cost	8,135	8,229
Materials and supplies, at average cost	8,852	7,380
Prepayments and other	7,294	5,352
Regulatory assets	3,981	3,483
Total current assets	74,950	74,757
Other long-term assets
Regulatory assets	119,108	120,863
Unamortized debt expense	84	23
Other	13,778	13,573
Other	132,970	134,459
Total assets	980,223	975,541
Capitalization
Common stock equity	291,760	291,291	295,275	292,702
Cumulative preferred stock—not subject to mandatory redemption	7,000	7,000
Long-term debt, net	213,677	213,703
Total capitalization	512,437	511,994
Current liabilities
Short-term borrowings from non-affiliates	0
Short-term borrowings from affiliate	0	0
Accounts payable	19,796	18,126
Interest and preferred dividends payable	3,806	4,206
Taxes accrued	23,394	28,100
Regulatory liabilities	713	2,219
Other	8,920	7,637
Total current liabilities	56,629	60,288
Deferred credits and other liabilities
Deferred income taxes	111,616	108,052
Regulatory liabilities	98,844	93,974
Unamortized tax credits	16,246	15,994
Defined benefit pension and other postretirement benefit plans liability	73,246	75,005
Other	13,803	13,024
Total deferred credits and other liabilities	313,755	306,049
Contributions in aid of construction	97,402	97,210
Total liabilities and shareholders’ equity	980,223	975,541
Maui Electric
Utility property, plant and equipment
Land	3,016	3,016
Plant and equipment	1,125,429	1,109,487
Less accumulated depreciation	(488,789)	(478,644)
Construction in progress	22,739	19,038
Utility property, plant and equipment, net	662,395	652,897
Nonutility property, plant and equipment, less accumulated depreciation	1,532	1,532
Total property, plant and equipment, net	663,927	654,429
Investment in wholly owned subsidiaries, at equity	0	0
Current assets
Cash and cash equivalents	5,389	2,048	2,372	5,385
Advances to affiliates	1,000	10,000
Customer accounts receivable, net	18,700	17,260
Accrued unbilled revenues, net	14,790	12,308
Other accounts receivable, net	1,042	1,416
Fuel oil stock, at average cost	12,768	10,962
Materials and supplies, at average cost	17,531	16,371
Prepayments and other	3,602	2,179
Regulatory assets	4,295	2,364
Total current assets	79,117	74,908
Other long-term assets
Regulatory assets	106,522	108,324
Unamortized debt expense	109	34
Other	14,045	13,592
Other	120,676	121,950
Total assets	863,720	851,287
Capitalization
Common stock equity	261,903	259,554	266,823	263,725
Cumulative preferred stock—not subject to mandatory redemption	5,000	5,000
Long-term debt, net	189,960	190,120
Total capitalization	456,863	454,674
Current liabilities
Short-term borrowings from non-affiliates	0
Short-term borrowings from affiliate	0	0
Accounts payable	18,593	13,319
Interest and preferred dividends payable	2,113	2,882
Taxes accrued	20,964	25,387
Regulatory liabilities	2,044	1,543
Other	14,786	12,501
Total current liabilities	58,500	55,632
Deferred credits and other liabilities
Deferred income taxes	106,023	100,911
Regulatory liabilities	32,897	31,845
Unamortized tax credits	15,603	15,123
Defined benefit pension and other postretirement benefit plans liability	78,858	80,263
Other	15,959	14,969
Total deferred credits and other liabilities	249,340	243,111
Contributions in aid of construction	99,017	97,870
Total liabilities and shareholders’ equity	863,720	851,287
Other subsidiaries
Utility property, plant and equipment
Land	0	0
Plant and equipment	0	0
Less accumulated depreciation	0	0
Construction in progress	0	0
Utility property, plant and equipment, net	0	0
Nonutility property, plant and equipment, less accumulated depreciation	0	0
Total property, plant and equipment, net	0	0
Investment in wholly owned subsidiaries, at equity	0	0
Current assets
Cash and cash equivalents	101	101	101	101
Advances to affiliates	0	0
Customer accounts receivable, net	0	0
Accrued unbilled revenues, net	0	0
Other accounts receivable, net	0	0
Fuel oil stock, at average cost	0	0
Materials and supplies, at average cost	0	0
Prepayments and other	0	0
Regulatory assets	0	0
Total current assets	101	101
Other long-term assets
Regulatory assets	0	0
Unamortized debt expense	0	0
Other	0	0
Other	0	0
Total assets	101	101
Capitalization
Common stock equity	101	101	101	101
Cumulative preferred stock—not subject to mandatory redemption	0	0
Long-term debt, net	0	0
Total capitalization	101	101
Current liabilities
Short-term borrowings from non-affiliates	0
Short-term borrowings from affiliate	0	0
Accounts payable	0	0
Interest and preferred dividends payable	0	0
Taxes accrued	0	0
Regulatory liabilities	0	0
Other	0	0
Total current liabilities	0	0
Deferred credits and other liabilities
Deferred income taxes	0	0
Regulatory liabilities	0	0
Unamortized tax credits	0	0
Defined benefit pension and other postretirement benefit plans liability	0	0
Other	0	0
Total deferred credits and other liabilities	0	0
Contributions in aid of construction	0	0
Total liabilities and shareholders’ equity	101	101
Consolidating adjustments
Utility property, plant and equipment
Land	0	0
Plant and equipment	0	0
Less accumulated depreciation	0	0
Construction in progress	0	0
Utility property, plant and equipment, net	0	0
Nonutility property, plant and equipment, less accumulated depreciation	0	0
Total property, plant and equipment, net	0	0
Investment in wholly owned subsidiaries, at equity	(553,764)	(550,946)
Current assets
Cash and cash equivalents	0	0	0	0
Advances to affiliates	(5,100)	(13,500)
Customer accounts receivable, net	0	0
Accrued unbilled revenues, net	0	0
Other accounts receivable, net	(9,536)	(6,280)
Fuel oil stock, at average cost	0	0
Materials and supplies, at average cost	0	0
Prepayments and other	(251)	(933)
Regulatory assets	0	0
Total current assets	(14,887)	(20,713)
Other long-term assets
Regulatory assets	0	0
Unamortized debt expense	0	0
Other	0	0
Other	0	0
Total assets	(568,651)	(571,659)
Capitalization
Common stock equity	(553,764)	(550,946)	(562,199)	(556,528)
Cumulative preferred stock—not subject to mandatory redemption	0	0
Long-term debt, net	0	0
Total capitalization	(553,764)	(550,946)
Current liabilities
Short-term borrowings from non-affiliates	0
Short-term borrowings from affiliate	(5,100)	(13,500)
Accounts payable	0	0
Interest and preferred dividends payable	(6)	(11)
Taxes accrued	(251)	(933)
Regulatory liabilities	0	0
Other	(9,530)	(6,269)
Total current liabilities	(14,887)	(20,713)
Deferred credits and other liabilities
Deferred income taxes	224	263
Regulatory liabilities	0	0
Unamortized tax credits	0	0
Defined benefit pension and other postretirement benefit plans liability	0	0
Other	(224)	(263)
Total deferred credits and other liabilities	0	0
Contributions in aid of construction	0	0
Total liabilities and shareholders’ equity	(568,651)	(571,659)
Hawaiian Electric Company, Inc. and Subsidiaries
Utility property, plant and equipment
Land	53,178	53,153
Plant and equipment	6,711,418	6,605,732
Less accumulated depreciation	(2,430,097)	(2,369,282)
Construction in progress	272,438	211,742
Utility property, plant and equipment, net	4,606,937	4,501,345
Nonutility property, plant and equipment, less accumulated depreciation	7,410	7,407
Total property, plant and equipment, net	4,614,347	4,508,752
Investment in wholly owned subsidiaries, at equity	0	0
Current assets
Cash and cash equivalents	42,582	74,286	27,579	24,449
Advances to affiliates	0	0
Customer accounts receivable, net	126,161	123,688
Accrued unbilled revenues, net	103,596	91,693
Other accounts receivable, net	3,684	5,233
Fuel oil stock, at average cost	72,392	66,430
Materials and supplies, at average cost	57,099	53,679
Prepayments and other	36,340	23,100
Regulatory assets	74,167	66,032
Total current assets	516,021	504,141
Other long-term assets
Regulatory assets	864,110	891,419
Unamortized debt expense	690	208
Other	75,987	70,908
Other	940,787	962,535
Total assets	6,071,155	5,975,428
Capitalization
Common stock equity	1,803,506	1,799,787	$ 1,743,006	$ 1,728,325
Cumulative preferred stock—not subject to mandatory redemption	34,293	34,293
Long-term debt, net	1,318,845	1,319,260
Total capitalization	3,156,644	3,153,340
Current liabilities
Short-term borrowings from non-affiliates	43,990	0
Short-term borrowings from affiliate	0	0
Accounts payable	162,375	117,814
Interest and preferred dividends payable	19,497	22,838
Taxes accrued	142,263	172,730
Regulatory liabilities	2,883	3,762
Other	53,140	55,221
Total current liabilities	424,148	372,365
Deferred credits and other liabilities
Deferred income taxes	759,972	733,659
Regulatory liabilities	428,747	406,931
Unamortized tax credits	91,386	88,961
Defined benefit pension and other postretirement benefit plans liability	587,718	599,726
Other	79,336	76,921
Total deferred credits and other liabilities	1,947,159	1,906,198
Contributions in aid of construction	543,204	543,525
Total liabilities and shareholders’ equity	$ 6,071,155	$ 5,975,428