Consolidating financial information (Details 3) - HECO (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Other long-term assets
Total assets	$ 9,904,827	$ 9,594,477
Capitalization
Cumulative preferred stock - not subject to mandatory redemption
Current liabilities
Interest and preferred dividends payable	27,907	25,041
Deferred credits and other liabilities
Deferred income taxes	438,886	354,051
Contributions in aid of construction	387,863	356,203
Total liabilities and shareholders' equity	9,904,827	9,594,477
HECO
Utility plant, at cost
Land	43,347	43,316
Plant and equipment	3,244,892	3,091,908
Less accumulated depreciation	(1,172,560)	(1,141,839)
Construction in progress	146,571	117,625
Net utility plant	2,262,250	2,111,010
Investment in wholly owned subsidiaries, at equity	527,791	516,143
Current assets
Cash and cash equivalents	6,982	44,819	8,847	121,019
Customer accounts receivable, net	166,597	130,190
Accrued unbilled revenues, net	99,901	103,328
Other accounts receivable, net	15,864	8,987
Fuel oil stock, at average cost	164,402	128,037
Materials and supplies, at average cost	31,416	25,096
Prepayments and other	47,458	22,517
Regulatory assets	22,693	18,038
Total current assets	555,313	481,012
Other long-term assets
Regulatory assets	512,576	478,851
Unamortized debt expense	7,227	8,446
Other	60,361	58,672
Total other long-term assets	580,164	545,969
Total assets	3,925,518	3,654,134
Capitalization
Common stock equity	1,443,338	1,402,841
Cumulative preferred stock - not subject to mandatory redemption	22,293	22,293
Long-term debt, net	780,546	629,757
Total capitalization	2,246,177	2,054,891
Current liabilities
Current portion of long-term debt		42,580
Short-term borrowings - nonaffiliates	44,719
Short-term borrowings-affiliate	36,400	64,650
Accounts payable	170,792	140,044
Interest and preferred dividends payable	15,122	12,648
Taxes accrued	164,498	155,867
Other	46,868	50,828
Total current liabilities	478,399	466,617
Deferred credits and other liabilities
Deferred income taxes	301,803	236,890
Regulatory liabilities	216,284	215,401
Unamortized tax credits	38,091	34,877
Retirement benefits liability	345,537	368,245
Other	69,109	72,418
Total deferred credits and other liabilities	970,824	927,831
Contributions in aid of construction	230,118	204,795
Total liabilities and shareholders' equity	3,925,518	3,654,134
HELCO
Utility plant, at cost
Land	5,182	5,182
Plant and equipment	1,066,465	1,048,599
Less accumulated depreciation	(431,229)	(414,769)
Construction in progress	15,963	8,144
Net utility plant	656,381	647,156
Current assets
Cash and cash equivalents	5,226	3,383	3,292	1,229
Advances to affiliates	29,400	46,150
Customer accounts receivable, net	35,074	28,602
Accrued unbilled revenues, net	15,392	18,499
Other accounts receivable, net	1,950	1,186
Fuel oil stock, at average cost	16,054	19,217
Materials and supplies, at average cost	5,419	4,700
Prepayments and other	7,314	6,948
Regulatory assets	1,236	1,115
Total current assets	117,065	129,800
Other long-term assets
Regulatory assets	89,736	86,394
Unamortized debt expense	2,100	2,464
Other	14,645	11,843
Total other long-term assets	106,481	100,701
Total assets	879,927	877,657
Capitalization
Common stock equity	286,462	280,468
Cumulative preferred stock - not subject to mandatory redemption	7,000	7,000
Long-term debt, net	201,323	204,110
Total capitalization	494,785	491,578
Current liabilities
Current portion of long-term debt		7,200
Accounts payable	23,283	29,616
Interest and preferred dividends payable	3,809	4,074
Taxes accrued	36,720	38,598
Other	15,135	9,478
Total current liabilities	78,947	88,966
Deferred credits and other liabilities
Deferred income taxes	69,344	61,044
Regulatory liabilities	66,077	62,049
Unamortized tax credits	13,190	12,951
Retirement benefits liability	57,390	62,036
Other	20,334	22,391
Total deferred credits and other liabilities	226,335	220,471
Contributions in aid of construction	79,860	76,642
Total liabilities and shareholders' equity	879,927	877,657
MECO
Utility plant, at cost
Land	3,015	3,016
Plant and equipment	934,412	911,520
Less accumulated depreciation	(422,661)	(410,286)
Construction in progress	13,682	13,069
Net utility plant	528,448	517,319
Current assets
Cash and cash equivalents	3,409	496	1,621	594
Advances to affiliates	7,000	18,500
Customer accounts receivable, net	25,262	24,536
Accrued unbilled revenues, net	16,797	15,999
Other accounts receivable, net	995	3,008
Fuel oil stock, at average cost	22,464	24,294
Materials and supplies, at average cost	13,658	13,392
Prepayments and other	9,234	7,343
Regulatory assets	1,174	1,130
Total current assets	99,993	108,698
Other long-term assets
Regulatory assets	88,579	83,861
Unamortized debt expense	1,459	1,876
Other	18,761	15,846
Total other long-term assets	108,799	101,583
Total assets	737,240	727,600
Capitalization
Common stock equity	241,225	235,568
Cumulative preferred stock - not subject to mandatory redemption	5,000	5,000
Long-term debt, net	166,000	166,703
Total capitalization	412,225	407,271
Current liabilities
Current portion of long-term debt		7,720
Accounts payable	17,924	18,920
Interest and preferred dividends payable	3,533	2,762
Taxes accrued	34,084	35,752
Other	17,458	13,603
Total current liabilities	72,999	78,757
Deferred credits and other liabilities
Deferred income taxes	49,577	39,929
Regulatory liabilities	36,969	38,016
Unamortized tax credits	12,897	12,786
Retirement benefits liability	60,672	64,840
Other	14,016	11,235
Total deferred credits and other liabilities	174,131	166,806
Contributions in aid of construction	77,885	74,766
Total liabilities and shareholders' equity	737,240	727,600
Other subsidiaries
Current assets
Cash and cash equivalents	105	108	109	94
Total current assets	105	108
Other long-term assets
Total assets	105	108
Capitalization
Common stock equity	104	107
Total capitalization	104	107
Current liabilities
Other	1	1
Total current liabilities	1	1
Deferred credits and other liabilities
Total liabilities and shareholders' equity	105	108
Consolidating adjustments
Utility plant, at cost
Investment in wholly owned subsidiaries, at equity	(527,791)	(516,143)
Current assets
Advances to affiliates	(36,400)	(64,650)
Other accounts receivable, net	(16,884)	(4,558)
Prepayments and other		(141)
Total current assets	(53,284)	(69,349)
Other long-term assets
Total assets	(581,075)	(585,492)
Capitalization
Common stock equity	(527,791)	(516,143)
Total capitalization	(527,791)	(516,143)
Current liabilities
Short-term borrowings-affiliate	(36,400)	(64,650)
Interest and preferred dividends payable	(6)	(1)
Taxes accrued		(141)
Other	(16,878)	(4,557)
Total current liabilities	(53,284)	(69,349)
Deferred credits and other liabilities
Total liabilities and shareholders' equity	(581,075)	(585,492)
HECO Consolidated
Utility plant, at cost
Land	51,544	51,514
Plant and equipment	5,245,769	5,052,027
Less accumulated depreciation	(2,026,450)	(1,966,894)
Construction in progress	176,216	138,838
Net utility plant	3,447,079	3,275,485
Current assets
Cash and cash equivalents	15,722	48,806	13,869	122,936
Customer accounts receivable, net	226,933	183,328
Accrued unbilled revenues, net	132,090	137,826
Other accounts receivable, net	1,925	8,623
Fuel oil stock, at average cost	202,920	171,548
Materials and supplies, at average cost	50,493	43,188
Prepayments and other	64,006	36,667
Regulatory assets	25,103	20,283
Total current assets	719,192	650,269
Other long-term assets
Regulatory assets	690,891	649,106
Unamortized debt expense	10,786	12,786
Other	93,767	86,361
Total other long-term assets	795,444	748,253
Total assets	4,961,715	4,674,007
Capitalization
Common stock equity	1,443,338	1,402,841		1,334,155
Cumulative preferred stock - not subject to mandatory redemption	34,293	34,293
Long-term debt, net	1,147,869	1,000,570
Total capitalization	2,625,500	2,437,704
Current liabilities
Current portion of long-term debt		57,500
Short-term borrowings - nonaffiliates	44,719
Accounts payable	211,999	188,580
Interest and preferred dividends payable	22,458	19,483
Taxes accrued	235,302	230,076
Other	62,584	69,353
Total current liabilities	577,062	564,992
Deferred credits and other liabilities
Deferred income taxes	420,724	337,863
Regulatory liabilities	319,330	315,466
Unamortized tax credits	64,178	60,614
Retirement benefits liability	463,599	495,121
Other	103,459	106,044
Total deferred credits and other liabilities	1,371,290	1,315,108
Contributions in aid of construction	387,863	356,203
Total liabilities and shareholders' equity	$ 4,961,715	$ 4,674,007