Consolidating financial information (Details 3) - HECO (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Other long-term assets
Total assets	$ 10,298,569	$ 10,149,132
Capitalization
Cumulative preferred stock - not subject to mandatory redemption
Current liabilities
Interest and preferred dividends payable	26,358	26,258
Deferred credits and other liabilities
Deferred income taxes	459,249	439,329
Contributions in aid of construction	415,795	405,520
Total liabilities and shareholders' equity	10,298,569	10,149,132
HECO
Utility plant, at cost
Land	43,400	43,370
Plant and equipment	3,377,351	3,325,862
Less accumulated depreciation	(1,198,256)	(1,185,899)
Construction in progress	123,898	130,143
Net utility plant	2,346,393	2,313,476
Investment in wholly owned subsidiaries, at equity	501,871	497,939
Current assets
Cash and cash equivalents	32,661	8,265	1,980	44,819
Advances to affiliates	13,000	9,400
Customer accounts receivable, net	139,540	154,316
Accrued unbilled revenues, net	102,307	100,600
Other accounts receivable, net	13,437	33,313
Fuel oil stock, at average cost	153,331	123,176
Materials and supplies, at average cost	33,632	31,779
Prepayments and other	26,668	21,708
Regulatory assets	50,315	42,675
Total current assets	564,891	525,232
Other long-term assets
Regulatory assets	601,447	601,451
Unamortized debt expense	6,844	7,042
Other	45,348	46,586
Total other long-term assets	653,639	655,079
Total assets	4,066,794	3,991,726
Capitalization
Common stock equity	1,476,513	1,472,136
Cumulative preferred stock - not subject to mandatory redemption	22,293	22,293
Long-term debt, net	780,547	780,546
Total capitalization	2,279,353	2,274,975
Current liabilities
Current portion of long-term debt	43,052
Short-term borrowings-affiliate	16,650	18,050
Accounts payable	181,266	134,651
Interest and preferred dividends payable	14,643	14,479
Taxes accrued	138,681	174,477
Other	49,186	47,203
Total current liabilities	443,478	388,860
Deferred credits and other liabilities
Deferred income taxes	316,153	302,569
Regulatory liabilities	220,715	218,437
Unamortized tax credits	41,111	39,827
Retirement benefits liability	453,573	459,765
Other	67,362	68,783
Total deferred credits and other liabilities	1,098,914	1,089,381
Contributions in aid of construction	245,049	238,510
Total liabilities and shareholders' equity	4,066,794	3,991,726
HELCO
Utility plant, at cost
Land	5,182	5,182
Plant and equipment	1,089,414	1,086,048
Less accumulated depreciation	(439,184)	(433,531)
Construction in progress	17,623	12,126
Net utility plant	673,035	669,825
Current assets
Cash and cash equivalents	2,770	5,441	2,676	3,383
Advances to affiliates	16,650	18,050
Customer accounts receivable, net	30,046	29,772
Accrued unbilled revenues, net	16,484	14,393
Other accounts receivable, net	861	1,122
Fuel oil stock, at average cost	13,429	15,485
Materials and supplies, at average cost	5,950	5,336
Prepayments and other	3,133	5,146
Regulatory assets	5,412	4,056
Total current assets	94,735	98,801
Other long-term assets
Regulatory assets	109,547	109,815
Unamortized debt expense	2,004	2,066
Other	9,057	9,871
Total other long-term assets	120,608	121,752
Total assets	888,378	890,378
Capitalization
Common stock equity	269,716	268,908
Cumulative preferred stock - not subject to mandatory redemption	7,000	7,000
Long-term debt, net	201,328	201,326
Total capitalization	478,044	477,234
Current liabilities
Accounts payable	26,534	27,457
Interest and preferred dividends payable	3,789	4,027
Taxes accrued	30,586	38,778
Other	11,989	10,310
Total current liabilities	72,898	80,572
Deferred credits and other liabilities
Deferred income taxes	71,233	68,479
Regulatory liabilities	68,878	67,359
Unamortized tax credits	13,428	13,450
Retirement benefits liability	79,421	80,686
Other	16,937	17,799
Total deferred credits and other liabilities	249,897	247,773
Contributions in aid of construction	87,539	84,799
Total liabilities and shareholders' equity	888,378	890,378
MECO
Utility plant, at cost
Land	3,016	3,016
Plant and equipment	961,168	952,490
Less accumulated depreciation	(425,370)	(421,359)
Construction in progress	12,148	9,109
Net utility plant	550,962	543,256
Current assets
Cash and cash equivalents	1,405	3,349	1,088	496
Customer accounts receivable, net	24,871	26,691
Accrued unbilled revenues, net	16,824	19,305
Other accounts receivable, net	1,341	3,016
Fuel oil stock, at average cost	23,931	22,758
Materials and supplies, at average cost	14,848	13,970
Prepayments and other	2,663	6,011
Regulatory assets	6,077	4,536
Total current assets	91,960	99,636
Other long-term assets
Regulatory assets	101,353	102,063
Unamortized debt expense	1,397	1,446
Other	14,861	14,848
Total other long-term assets	117,611	118,357
Total assets	760,533	761,249
Capitalization
Common stock equity	232,051	228,927
Cumulative preferred stock - not subject to mandatory redemption	5,000	5,000
Long-term debt, net	166,000	166,000
Total capitalization	403,051	399,927
Current liabilities
Short-term borrowings-affiliate	13,000	9,400
Accounts payable	20,626	24,716
Interest and preferred dividends payable	3,274	2,593
Taxes accrued	30,292	37,811
Other	16,586	14,634
Total current liabilities	83,778	89,154
Deferred credits and other liabilities
Deferred income taxes	48,212	46,563
Regulatory liabilities	35,934	36,278
Unamortized tax credits	13,400	13,307
Retirement benefits liability	78,684	79,754
Other	14,267	14,055
Total deferred credits and other liabilities	190,497	189,957
Contributions in aid of construction	83,207	82,211
Total liabilities and shareholders' equity	760,533	761,249
Other subsidiaries
Current assets
Cash and cash equivalents	104	104	106	108
Total current assets	104	104
Other long-term assets
Total assets	104	104
Capitalization
Common stock equity	104	104
Total capitalization	104	104
Deferred credits and other liabilities
Total liabilities and shareholders' equity	104	104
Consolidating adjustments
Utility plant, at cost
Investment in wholly owned subsidiaries, at equity	(501,871)	(497,939)
Current assets
Advances to affiliates	(29,650)	(27,450)
Other accounts receivable, net	(9,844)	(9,275)
Prepayments and other	(209)
Total current assets	(39,703)	(36,725)
Other long-term assets
Total assets	(541,574)	(534,664)
Capitalization
Common stock equity	(501,871)	(497,939)
Total capitalization	(501,871)	(497,939)
Current liabilities
Short-term borrowings-affiliate	(29,650)	(27,450)
Interest and preferred dividends payable	(13)	(7)
Taxes accrued	(209)
Other	(9,831)	(9,268)
Total current liabilities	(39,703)	(36,725)
Deferred credits and other liabilities
Total liabilities and shareholders' equity	(541,574)	(534,664)
HECO Consolidated
Utility plant, at cost
Land	51,598	51,568
Plant and equipment	5,427,933	5,364,400
Less accumulated depreciation	(2,062,810)	(2,040,789)
Construction in progress	153,669	151,378
Net utility plant	3,570,390	3,526,557
Current assets
Cash and cash equivalents	36,940	17,159	5,850	48,806
Customer accounts receivable, net	194,457	210,779
Accrued unbilled revenues, net	135,615	134,298
Other accounts receivable, net	5,795	28,176
Fuel oil stock, at average cost	190,691	161,419
Materials and supplies, at average cost	54,430	51,085
Prepayments and other	32,255	32,865
Regulatory assets	61,804	51,267
Total current assets	711,987	687,048
Other long-term assets
Regulatory assets	812,347	813,329
Unamortized debt expense	10,245	10,554
Other	69,266	71,305
Total other long-term assets	891,858	895,188
Total assets	5,174,235	5,108,793
Capitalization
Common stock equity	1,476,513	1,472,136
Cumulative preferred stock - not subject to mandatory redemption	34,293	34,293
Long-term debt, net	1,147,875	1,147,872
Total capitalization	2,658,681	2,654,301
Current liabilities
Current portion of long-term debt	43,052
Accounts payable	228,426	186,824
Interest and preferred dividends payable	21,693	21,092
Taxes accrued	199,350	251,066
Other	67,930	62,879
Total current liabilities	560,451	521,861
Deferred credits and other liabilities
Deferred income taxes	435,598	417,611
Regulatory liabilities	325,527	322,074
Unamortized tax credits	67,939	66,584
Retirement benefits liability	611,678	620,205
Other	98,566	100,637
Total deferred credits and other liabilities	1,539,308	1,527,111
Contributions in aid of construction	415,795	405,520
Total liabilities and shareholders' equity	$ 5,174,235	$ 5,108,793