Electric utility segment Consolidating Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Utility property, plant and equipment
Total property, plant and equipment, net	$ 4,377,658	$ 4,148,774
Other long-term assets
Total assets	11,790,196	11,185,142	$ 10,340,906
Capitalization
Total shareholders' equity	1,927,640	1,790,573	1,726,406	$ 1,593,008
Cumulative preferred stock – not subject to mandatory redemption	0	0
Liabilities
Interest and dividends payable	26,042	25,336
Deferred credits and other liabilities
Deferred income taxes		633,570
Contributions in aid of construction	506,087	466,432
Total capitalization and liabilities	11,790,196	11,185,142
HECO
Utility property, plant and equipment
Land	43,557	43,819
Plant and equipment	4,026,079	3,782,438
Less accumulated depreciation	(1,316,467)	(1,253,866)
Construction in progress	147,979	134,376
Utility property, plant and equipment, net	2,901,148	2,706,767
Nonutility property, plant and equipment, less accumulated depreciation	5,659	4,950
Total property, plant and equipment, net	2,906,807	2,711,717
Investment in wholly-owned subsidiaries, at equity	556,528	538,639
Assets, Current [Abstract]
Cash and cash equivalents	16,281	12,416	61,245	8,265
Advances to affiliates	0	16,100
Customer accounts receivable, net	93,515	111,462
Accrued unbilled revenues, net	60,080	103,072
Other accounts receivable, net	16,421	9,980
Fuel oil stock, at average cost	49,455	74,515
Materials and supplies, at average cost	30,921	33,154
Prepayments and other	25,505	20,231
Regulatory assets	63,615	58,550
Total current assets	355,793	439,480
Other long-term assets
Regulatory assets	608,957	623,784
Unamortized debt expense	5,742	5,640
Other	47,731	53,106
Total other long-term assets	662,430	682,530
Total assets	4,481,558	4,372,366
Capitalization
Total shareholders' equity	1,728,325	1,682,144	1,593,564	1,472,136
Cumulative preferred stock – not subject to mandatory redemption	22,293	22,293
Long-term debt, net	880,546	830,546
Total capitalization	2,631,164	2,534,983
Liabilities
Short-term borrowings-affiliate	23,000	0
Accounts payable	84,631	122,433
Interest and dividends payable	15,747	15,407
Taxes accrued	131,668	176,339
Regulatory liabilities	0	191
Other	41,083	45,369
Total current liabilities	296,129	359,739
Deferred credits and other liabilities
Deferred income taxes	466,133	407,979
Regulatory liabilities	254,033	236,727
Unamortized tax credits	54,078	49,865
Defined benefit pension and other postretirement benefit plans liability	409,021	446,888
Other	51,273	52,446
Total deferred credits and other liabilities	1,234,538	1,193,905
Contributions in aid of construction	319,727	283,739
Total capitalization and liabilities	4,481,558	4,372,366
Consolidating adjustments
Utility property, plant and equipment
Nonutility property, plant and equipment, less accumulated depreciation	0
Investment in wholly-owned subsidiaries, at equity	(556,528)	(538,639)
Assets, Current [Abstract]
Advances to affiliates	(23,000)	(16,100)
Other accounts receivable, net	(8,962)	(8,924)
Prepayments and other	(251)	(475)
Total current assets	(32,213)	(25,499)
Other long-term assets
Regulatory assets	0	(183)
Total other long-term assets	0	(183)
Total assets	(588,741)	(564,321)
Capitalization
Total shareholders' equity	(556,528)	(538,639)	(523,674)	(497,939)
Total capitalization	(556,528)	(538,639)
Liabilities
Short-term borrowings-affiliate	(23,000)	(16,100)
Interest and dividends payable	(4)	(11)
Taxes accrued	(251)	(292)
Regulatory liabilities		0
Other	(8,958)	(9,096)
Total current liabilities	(32,213)	(25,499)
Deferred credits and other liabilities
Deferred income taxes	286
Regulatory liabilities	0	(183)
Defined benefit pension and other postretirement benefit plans liability	0
Other	(286)
Total deferred credits and other liabilities	0	(183)
Total capitalization and liabilities	(588,741)	(564,321)
HELCO
Utility property, plant and equipment
Land	6,219	5,464
Plant and equipment	1,212,195	1,179,032
Less accumulated depreciation	(486,028)	(473,933)
Construction in progress	11,455	12,421
Utility property, plant and equipment, net	743,841	722,984
Nonutility property, plant and equipment, less accumulated depreciation	82	82
Total property, plant and equipment, net	743,923	723,066
Assets, Current [Abstract]
Cash and cash equivalents	2,682	612	1,326	5,441
Advances to affiliates	15,500	0
Customer accounts receivable, net	20,508	24,222
Accrued unbilled revenues, net	12,531	15,926
Other accounts receivable, net	1,275	981
Fuel oil stock, at average cost	8,310	13,800
Materials and supplies, at average cost	6,865	6,664
Prepayments and other	9,091	10,137
Regulatory assets	4,501	6,745
Total current assets	81,263	79,087
Other long-term assets
Regulatory assets	114,562	107,454
Unamortized debt expense	1,494	1,438
Other	14,693	15,366
Total other long-term assets	130,749	124,258
Total assets	955,935	926,411
Capitalization
Total shareholders' equity	292,702	281,846	274,802	268,908
Cumulative preferred stock – not subject to mandatory redemption	7,000	7,000
Long-term debt, net	215,000	190,000
Total capitalization	514,702	478,846
Liabilities
Short-term borrowings-affiliate	0	10,500
Accounts payable	17,702	23,728
Interest and dividends payable	4,255	3,989
Taxes accrued	30,342	37,548
Regulatory liabilities	1,030	0
Other	8,760	9,587
Total current liabilities	62,089	85,352
Deferred credits and other liabilities
Deferred income taxes	100,681	91,924
Regulatory liabilities	84,623	77,707
Unamortized tax credits	15,406	14,902
Defined benefit pension and other postretirement benefit plans liability	69,893	72,547
Other	13,243	10,658
Total deferred credits and other liabilities	283,846	267,738
Contributions in aid of construction	95,298	94,475
Total capitalization and liabilities	955,935	926,411
MECO
Utility property, plant and equipment
Land	3,016	3,016
Plant and equipment	1,077,424	1,048,012
Less accumulated depreciation	(463,509)	(447,711)
Construction in progress	15,875	11,819
Utility property, plant and equipment, net	632,806	615,136
Nonutility property, plant and equipment, less accumulated depreciation	1,531	1,531
Total property, plant and equipment, net	634,337	616,667
Assets, Current [Abstract]
Cash and cash equivalents	5,385	633	153	3,349
Advances to affiliates	7,500	0
Customer accounts receivable, net	18,755	22,800
Accrued unbilled revenues, net	11,898	18,376
Other accounts receivable, net	1,674	2,246
Fuel oil stock, at average cost	13,451	17,731
Materials and supplies, at average cost	16,643	17,432
Prepayments and other	2,295	3,575
Regulatory assets	4,115	6,126
Total current assets	81,716	88,919
Other long-term assets
Regulatory assets	100,981	102,788
Unamortized debt expense	1,105	1,245
Other	13,062	13,366
Total other long-term assets	115,148	117,399
Total assets	831,201	822,985
Capitalization
Total shareholders' equity	263,725	256,692	248,771	228,927
Cumulative preferred stock – not subject to mandatory redemption	5,000	5,000
Long-term debt, net	191,000	186,000
Total capitalization	459,725	447,692
Liabilities
Short-term borrowings-affiliate	0	5,600
Accounts payable	12,513	17,773
Interest and dividends payable	3,113	2,931
Taxes accrued	29,325	36,807
Regulatory liabilities	1,174	441
Other	13,194	15,804
Total current liabilities	59,319	79,356
Deferred credits and other liabilities
Deferred income taxes	87,706	73,536
Regulatory liabilities	30,683	29,966
Unamortized tax credits	14,730	14,725
Defined benefit pension and other postretirement benefit plans liability	74,060	75,960
Other	13,916	13,532
Total deferred credits and other liabilities	221,095	207,719
Contributions in aid of construction	91,062	88,218
Total capitalization and liabilities	831,201	822,985
HECO Consolidated
Utility property, plant and equipment
Land	52,792	52,299
Plant and equipment	6,315,698	6,009,482
Less accumulated depreciation	(2,266,004)	(2,175,510)
Construction in progress	175,309	158,616
Utility property, plant and equipment, net	4,277,795	4,044,887
Nonutility property, plant and equipment, less accumulated depreciation	7,272	6,563
Total property, plant and equipment, net	4,285,067	4,051,450
Investment in wholly-owned subsidiaries, at equity	0
Assets, Current [Abstract]
Cash and cash equivalents	24,449	13,762	62,825	17,159
Customer accounts receivable, net	132,778	158,484
Accrued unbilled revenues, net	84,509	137,374
Other accounts receivable, net	10,408	4,283
Fuel oil stock, at average cost	71,216	106,046
Materials and supplies, at average cost	54,429	57,250
Prepayments and other	36,640	33,468
Regulatory assets	72,231	71,421
Total current assets	486,660	582,088
Other long-term assets
Regulatory assets	824,500	833,843
Unamortized debt expense	8,341	8,323
Other	75,486	81,838
Total other long-term assets	908,327	924,004
Total assets	5,680,054	5,557,542
Capitalization
Total shareholders' equity	1,728,325	1,682,144	1,593,564	1,472,136
Cumulative preferred stock – not subject to mandatory redemption	34,293	34,293
Long-term debt, net	1,286,546	1,206,546
Total capitalization	3,049,164	2,922,983
Liabilities
Accounts payable	114,846	163,934
Interest and dividends payable	23,111	22,316
Taxes accrued	191,084	250,402
Regulatory liabilities	2,204	632
Other	54,079	61,664
Total current liabilities	385,324	498,948
Deferred credits and other liabilities
Deferred income taxes	654,806	573,439
Regulatory liabilities	369,339	344,217
Unamortized tax credits	84,214	79,492
Defined benefit pension and other postretirement benefit plans liability	552,974	595,395
Other	78,146	76,636
Total deferred credits and other liabilities	1,739,479	1,669,179
Contributions in aid of construction	506,087	466,432
Total capitalization and liabilities	5,680,054	5,557,542
Other subsidiaries
Assets, Current [Abstract]
Cash and cash equivalents	101	101	101	104
Total current assets	101	101
Other long-term assets
Total assets	101	101
Capitalization
Total shareholders' equity	101	101	$ 101	$ 104
Total capitalization	101	101
Liabilities
Other		0
Total current liabilities		0
Deferred credits and other liabilities
Total capitalization and liabilities	$ 101	$ 101