Electric utility segment - Consolidating balance sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Utility property, plant and equipment
Total property, plant and equipment, net	$ 4,482,990	$ 4,377,658
Other long-term assets
Total assets	11,979,239	11,782,018
Capitalization
Common stock equity	1,966,182	1,927,640	$ 1,898,520	$ 1,790,573
Cumulative preferred stock — not subject to mandatory redemption	0	0
Current liabilities
Interest and preferred dividends payable	23,490	26,042
Deferred credits and other liabilities
Deferred income taxes	712,199	680,877
Contributions in aid of construction	516,750	506,087
Total liabilities and shareholders’ equity	11,979,239	11,782,018
Hawaiian Electric Company
Utility property, plant and equipment
Land	43,945	43,557
Plant and equipment	4,098,246	4,026,079
Less accumulated depreciation	(1,344,064)	(1,316,467)
Construction in progress	188,057	147,979
Utility property, plant and equipment, net	2,986,184	2,901,148
Nonutility property, plant and equipment, less accumulated depreciation	5,761	5,659
Total property, plant and equipment, net	2,991,945	2,906,807
Investment in wholly owned subsidiaries, at equity	562,199	556,528
Current assets
Cash and cash equivalents	19,842	16,281	3,393	12,416
Advances to affiliates	0	0
Customer accounts receivable, net	79,632	93,515
Accrued unbilled revenues, net	63,021	60,080
Other accounts receivable, net	10,897	16,421
Fuel oil stock, at average cost	43,440	49,455
Materials and supplies, at average cost	32,669	30,921
Prepayments and other	15,495	25,505
Regulatory assets	83,235	63,615
Total current assets	348,231	355,793
Other long-term assets
Regulatory assets	583,486	608,957
Unamortized debt expense	249	359
Other	46,537	47,731
Total other long-term assets	630,272	657,047
Total assets	4,532,647	4,476,175
Capitalization
Common stock equity	1,743,006	1,728,325	1,696,658	1,682,144
Cumulative preferred stock — not subject to mandatory redemption	22,293	22,293
Long-term debt, net	875,443	875,163
Total capitalization	2,640,742	2,625,781
Current liabilities
Short-term borrowings from non-affiliates	36,995
Short-term borrowings from affiliate	37,000	23,000
Accounts payable	77,858	84,631
Interest and preferred dividends payable	14,441	15,747
Taxes accrued	95,703	131,668
Regulatory liabilities	0	0
Other	40,066	41,083
Total current liabilities	302,063	296,129
Deferred credits and other liabilities
Deferred income taxes	492,156	466,133
Regulatory liabilities	266,592	254,033
Unamortized tax credits	56,813	54,078
Defined benefit pension and other postretirement benefit plans liability	400,713	409,021
Other	50,055	51,273
Total deferred credits and other liabilities	1,266,329	1,234,538
Contributions in aid of construction	323,513	319,727
Total liabilities and shareholders’ equity	4,532,647	4,476,175
HELCO
Utility property, plant and equipment
Land	6,214	6,219
Plant and equipment	1,218,424	1,212,195
Less accumulated depreciation	(497,241)	(486,028)
Construction in progress	23,420	11,455
Utility property, plant and equipment, net	750,817	743,841
Nonutility property, plant and equipment, less accumulated depreciation	82	82
Total property, plant and equipment, net	750,899	743,923
Current assets
Cash and cash equivalents	5,264	2,682	801	612
Advances to affiliates	18,500	15,500
Customer accounts receivable, net	18,376	20,508
Accrued unbilled revenues, net	11,897	12,531
Other accounts receivable, net	1,400	1,275
Fuel oil stock, at average cost	7,386	8,310
Materials and supplies, at average cost	7,573	6,865
Prepayments and other	5,456	9,091
Regulatory assets	4,891	4,501
Total current assets	80,743	81,263
Other long-term assets
Regulatory assets	111,731	114,562
Unamortized debt expense	46	74
Other	13,423	14,693
Total other long-term assets	125,200	129,329
Total assets	956,842	954,515
Capitalization
Common stock equity	295,275	292,702	285,104	281,846
Cumulative preferred stock — not subject to mandatory redemption	7,000	7,000
Long-term debt, net	213,640	213,580
Total capitalization	515,915	513,282
Current liabilities
Short-term borrowings from affiliate	0	0
Accounts payable	12,786	17,702
Interest and preferred dividends payable	4,115	4,255
Taxes accrued	24,227	30,342
Regulatory liabilities	2,658	1,030
Other	9,639	8,760
Total current liabilities	53,425	62,089
Deferred credits and other liabilities
Deferred income taxes	103,430	100,681
Regulatory liabilities	89,774	84,623
Unamortized tax credits	17,308	15,406
Defined benefit pension and other postretirement benefit plans liability	68,241	69,893
Other	13,509	13,243
Total deferred credits and other liabilities	292,262	283,846
Contributions in aid of construction	95,240	95,298
Total liabilities and shareholders’ equity	956,842	954,515
Maui Electric
Utility property, plant and equipment
Land	3,016	3,016
Plant and equipment	1,094,874	1,077,424
Less accumulated depreciation	(473,438)	(463,509)
Construction in progress	18,666	15,875
Utility property, plant and equipment, net	643,118	632,806
Nonutility property, plant and equipment, less accumulated depreciation	1,532	1,531
Total property, plant and equipment, net	644,650	634,337
Current assets
Cash and cash equivalents	2,372	5,385	175	633
Advances to affiliates	18,500	7,500
Customer accounts receivable, net	18,257	18,755
Accrued unbilled revenues, net	12,806	11,898
Other accounts receivable, net	1,442	1,674
Fuel oil stock, at average cost	10,746	13,451
Materials and supplies, at average cost	16,669	16,643
Prepayments and other	1,693	2,295
Regulatory assets	2,345	4,115
Total current assets	84,830	81,716
Other long-term assets
Regulatory assets	99,426	100,981
Unamortized debt expense	49	64
Other	12,465	13,062
Total other long-term assets	111,940	114,107
Total assets	841,420	830,160
Capitalization
Common stock equity	266,823	263,725	258,146	256,692
Cumulative preferred stock — not subject to mandatory redemption	5,000	5,000
Long-term debt, net	190,040	189,959
Total capitalization	461,863	458,684
Current liabilities
Short-term borrowings from affiliate	0	0
Accounts payable	15,877	12,513
Interest and preferred dividends payable	2,764	3,113
Taxes accrued	21,983	29,325
Regulatory liabilities	710	1,174
Other	12,824	13,194
Total current liabilities	54,158	59,319
Deferred credits and other liabilities
Deferred income taxes	93,607	87,706
Regulatory liabilities	31,269	30,683
Unamortized tax credits	15,055	14,730
Defined benefit pension and other postretirement benefit plans liability	72,702	74,060
Other	14,769	13,916
Total deferred credits and other liabilities	227,402	221,095
Contributions in aid of construction	97,997	91,062
Total liabilities and shareholders’ equity	841,420	830,160
Other subsidiaries
Current assets
Cash and cash equivalents	101	101	101	101
Total current assets	101	101
Other long-term assets
Total assets	101	101
Capitalization
Common stock equity	101	101	101	101
Total capitalization	101	101
Deferred credits and other liabilities
Total liabilities and shareholders’ equity	101	101
Consolidating adjustments
Utility property, plant and equipment
Investment in wholly owned subsidiaries, at equity	(562,199)	(556,528)
Current assets
Cash and cash equivalents	0	0	0	0
Advances to affiliates	(37,000)	(23,000)
Other accounts receivable, net	(9,193)	(8,962)
Prepayments and other	(765)	(251)
Total current assets	(46,958)	(32,213)
Other long-term assets
Regulatory assets	0	0
Total other long-term assets	0	0
Total assets	(609,157)	(588,741)
Capitalization
Common stock equity	(562,199)	(556,528)	(543,351)	(538,639)
Total capitalization	(562,199)	(556,528)
Current liabilities
Short-term borrowings from affiliate	(37,000)	(23,000)
Interest and preferred dividends payable	(11)	(4)
Taxes accrued	(765)	(251)
Regulatory liabilities	0	0
Other	(9,182)	(8,958)
Total current liabilities	(46,958)	(32,213)
Deferred credits and other liabilities
Deferred income taxes	289	286
Regulatory liabilities	0	0
Defined benefit pension and other postretirement benefit plans liability	0
Other	(289)	(286)
Total deferred credits and other liabilities	0	0
Total liabilities and shareholders’ equity	(609,157)	(588,741)
Hawaiian Electric Company, Inc. and Subsidiaries
Utility property, plant and equipment
Land	53,175	52,792
Plant and equipment	6,411,544	6,315,698
Less accumulated depreciation	(2,314,743)	(2,266,004)
Construction in progress	230,143	175,309
Utility property, plant and equipment, net	4,380,119	4,277,795
Nonutility property, plant and equipment, less accumulated depreciation	7,375	7,272
Total property, plant and equipment, net	4,387,494	4,285,067
Current assets
Cash and cash equivalents	27,579	24,449	4,470	13,762
Advances to affiliates	0
Customer accounts receivable, net	116,265	132,778
Accrued unbilled revenues, net	87,724	84,509
Other accounts receivable, net	4,546	10,408
Fuel oil stock, at average cost	61,572	71,216
Materials and supplies, at average cost	56,911	54,429
Prepayments and other	21,879	36,640
Regulatory assets	90,471	72,231
Total current assets	466,947	486,660
Other long-term assets
Regulatory assets	794,643	824,500
Unamortized debt expense	344	497
Other	72,425	75,486
Total other long-term assets	867,412	900,483
Total assets	5,721,853	5,672,210
Capitalization
Common stock equity	1,743,006	1,728,325	$ 1,696,658	$ 1,682,144
Cumulative preferred stock — not subject to mandatory redemption	34,293	34,293
Long-term debt, net	1,279,123	1,278,702
Total capitalization	3,056,422	3,041,320
Current liabilities
Short-term borrowings from non-affiliates	36,995	0
Accounts payable	106,521	114,846
Interest and preferred dividends payable	21,309	23,111
Taxes accrued	141,148	191,084
Regulatory liabilities	3,368	2,204
Other	53,347	54,079
Total current liabilities	362,688	385,324
Deferred credits and other liabilities
Deferred income taxes	689,482	654,806
Regulatory liabilities	387,635	369,339
Unamortized tax credits	89,176	84,214
Defined benefit pension and other postretirement benefit plans liability	541,656	552,974
Other	78,044	78,146
Total deferred credits and other liabilities	1,785,993	1,739,479
Contributions in aid of construction	516,750	506,087
Total liabilities and shareholders’ equity	$ 5,721,853	$ 5,672,210