Consolidating financial information (Details 5) - HECO (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities
Net income (loss)	$ 41,061	$ 39,273	$ 75,213	$ 78,062
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation of property, plant and equipment			79,843	75,517
Other amortization			2,868	2,999
Change in deferred income taxes			40,403	41,541
Allowance for equity funds used during construction	(1,560)	(1,997)	(2,775)	(3,937)
Changes in assets and liabilities
Decrease (increase) in fuel oil stock			43,974	(35,893)
Increase in regulatory assets			(37,586)	(35,476)
Changes in prepaid and accrued income taxes and revenue taxes			(33,822)	(12,998)
Contributions to defined benefit pension and other postretirement benefit plans			(41,521)	(53,356)
Other increase in defined benefit pension and other postretirement benefit plans liability			41,191	31,204
Net cash provided by (used in) operating activities			130,792	(3,572)
Cash flows from investing activities
Capital expenditures			(158,830)	(145,263)
Contributions in aid of construction			17,188	26,981
Other			2,364
Net cash used in investing activities			(240,285)	(188,313)
Cash flows from financing activities
Common stock dividends			(48,921)	(47,851)
Proceeds from issuance of long-term debt			50,000	417,000
Repayment of long-term debt			(50,000)	(328,500)
Net increase in short-term borrowings from nonaffiliates and affiliate with original maturities of three months or less			42,093	27,419
Other			606	(2,055)
Net cash provided by financing activities			43,543	129,169
Net decrease in cash and cash equivalents			(65,950)	(62,716)
HECO
Cash flows from operating activities
Net income (loss)	28,963	29,646	53,662	57,216
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in earnings			(19,702)	(16,790)
Common stock dividends received from subsidiaries			14,227	10,967
Depreciation of property, plant and equipment			49,708	45,308
Other amortization			(160)	347
Change in deferred income taxes			27,560	31,673
Changes in tax credits, net			2,598	2,641
Allowance for equity funds used during construction	(1,247)	(1,654)	(2,230)	(3,235)
Changes in assets and liabilities
Decrease (increase) in accounts receivable			35,431	(17,653)
Decrease (Increase) in accrued unbilled revenues			(2,095)	(21,274)
Decrease (increase) in fuel oil stock			38,428	(28,905)
Increase in materials and supplies			(4,069)	(6,172)
Increase in regulatory assets			(25,647)	(28,190)
Increase (decrease) in accounts payable			(36,971)	12,843
Changes in prepaid and accrued income taxes and revenue taxes			(25,831)	(9,994)
Contributions to defined benefit pension and other postretirement benefit plans			(29,766)	(38,693)
Other increase in defined benefit pension and other postretirement benefit plans liability			30,929	22,947
Change in other assets and liabilities			(12,731)	(26,968)
Net cash provided by (used in) operating activities			93,341	(13,932)
Cash flows from investing activities
Capital expenditures			(104,846)	(111,011)
Contributions in aid of construction			11,924	23,693
Other			623
Advances from (to) affiliates			(8,600)	(8,700)
Net cash used in investing activities			(100,899)	(96,018)
Cash flows from financing activities
Common stock dividends			(40,789)	(36,522)
Preferred stock dividends of HECO and subsidiaries			(540)	(540)
Proceeds from issuance of long-term debt				327,000
Repayment of long-term debt				(219,580)
Net increase in short-term borrowings from nonaffiliates and affiliate with original maturities of three months or less			45,542	(1,058)
Other			(6)	(1,746)
Net cash provided by financing activities			4,207	67,554
Net decrease in cash and cash equivalents			(3,351)	(42,396)
Cash and cash equivalents, beginning of period			8,265	44,819
Cash and cash equivalents, end of period	4,914	2,423	4,914	2,423
HELCO
Cash flows from operating activities
Net income (loss)	5,013	4,624	9,567	11,369
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation of property, plant and equipment			17,094	16,737
Other amortization			716	1,418
Change in deferred income taxes			5,584	5,857
Changes in tax credits, net			70	125
Allowance for equity funds used during construction	(192)	(160)	(330)	(285)
Changes in assets and liabilities
Decrease (increase) in accounts receivable			(2,281)	(137)
Decrease (Increase) in accrued unbilled revenues			(2,848)	(6,456)
Decrease (increase) in fuel oil stock			5,812	(514)
Increase in materials and supplies			(1,480)	(1,022)
Increase in regulatory assets			(4,852)	(3,234)
Increase (decrease) in accounts payable			(2,513)	(6,938)
Changes in prepaid and accrued income taxes and revenue taxes			(6,171)	(6,347)
Contributions to defined benefit pension and other postretirement benefit plans			(5,389)	(6,536)
Other increase in defined benefit pension and other postretirement benefit plans liability			5,261	4,089
Change in other assets and liabilities			(3,171)	(3,432)
Net cash provided by (used in) operating activities			15,069	4,694
Cash flows from investing activities
Capital expenditures			(22,367)	(17,405)
Contributions in aid of construction			4,270	2,327
Advances from (to) affiliates			8,450	26,800
Net cash used in investing activities			(9,647)	11,722
Cash flows from financing activities
Common stock dividends			(7,194)	(6,569)
Preferred stock dividends of HECO and subsidiaries			(267)	(267)
Proceeds from issuance of long-term debt				31,000
Repayment of long-term debt				(41,200)
Other			(1)	171
Net cash provided by financing activities			(7,462)	(16,865)
Net decrease in cash and cash equivalents			(2,040)	(449)
Cash and cash equivalents, beginning of period			5,441	3,383
Cash and cash equivalents, end of period	3,401	2,934	3,401	2,934
MECO
Cash flows from operating activities
Net income (loss)	3,884	3,856	10,544	5,831
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation of property, plant and equipment			10,068	10,570
Other amortization			2,328	1,005
Change in deferred income taxes			5,636	4,994
Changes in tax credits, net			329	114
Allowance for equity funds used during construction	(121)	(183)	(215)	(417)
Changes in assets and liabilities
Decrease (increase) in accounts receivable			(318)	(702)
Decrease (Increase) in accrued unbilled revenues			54	(4,323)
Decrease (increase) in fuel oil stock			(266)	(6,474)
Increase in materials and supplies			(1,590)	(405)
Increase in regulatory assets			(7,087)	(4,052)
Increase (decrease) in accounts payable			(1,750)	26
Changes in prepaid and accrued income taxes and revenue taxes			(6,121)	(4,800)
Contributions to defined benefit pension and other postretirement benefit plans			(5,431)	(6,857)
Other increase in defined benefit pension and other postretirement benefit plans liability			5,385	4,130
Change in other assets and liabilities			5,929	18
Net cash provided by (used in) operating activities			17,495	(1,342)
Cash flows from investing activities
Capital expenditures			(23,038)	(13,202)
Contributions in aid of construction			994	961
Advances from (to) affiliates				18,500
Net cash used in investing activities			(22,044)	6,259
Cash flows from financing activities
Common stock dividends			(7,008)	(4,373)
Preferred stock dividends of HECO and subsidiaries			(191)	(191)
Proceeds from issuance of long-term debt				59,000
Repayment of long-term debt				(67,720)
Net increase in short-term borrowings from nonaffiliates and affiliate with original maturities of three months or less			8,600	8,700
Other			(2)	(354)
Net cash provided by financing activities			1,399	(4,938)
Net decrease in cash and cash equivalents			(3,150)	(21)
Cash and cash equivalents, beginning of period			3,349	496
Cash and cash equivalents, end of period	199	475	199	475
Other subsidiaries
Cash flows from operating activities
Net income (loss)	(1)	(1)	(1)	(2)
Changes in assets and liabilities
Change in other assets and liabilities				(1)
Net cash provided by (used in) operating activities			(1)	(3)
Cash flows from financing activities
Net decrease in cash and cash equivalents			(1)	(3)
Cash and cash equivalents, beginning of period			104	108
Cash and cash equivalents, end of period	103	105	103	105
Consolidating adjustments
Cash flows from operating activities
Net income (loss)	(8,667)	(8,250)	(19,652)	(16,740)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in earnings			19,652	16,740
Common stock dividends received from subsidiaries			(14,202)	(10,942)
Changes in assets and liabilities
Decrease (increase) in accounts receivable			(579)	7,534
Change in other assets and liabilities			579	(7,534)
Net cash provided by (used in) operating activities			(14,202)	(10,942)
Cash flows from investing activities
Advances from (to) affiliates			150	(36,600)
Net cash used in investing activities			150	(36,600)
Cash flows from financing activities
Common stock dividends			14,202	10,942
Net increase in short-term borrowings from nonaffiliates and affiliate with original maturities of three months or less			(150)	36,600
Net cash provided by financing activities			14,052	47,542
HECO Consolidated
Cash flows from operating activities
Net income (loss)	29,192	29,875	54,120	57,674
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in earnings			(50)	(50)
Common stock dividends received from subsidiaries			25	25
Depreciation of property, plant and equipment			76,870	72,615
Other amortization			2,884	2,770
Change in deferred income taxes			38,780	42,524
Changes in tax credits, net			2,997	2,880
Allowance for equity funds used during construction	(1,560)	(1,997)	(2,775)	(3,937)
Changes in assets and liabilities
Decrease (increase) in accounts receivable			32,253	(10,958)
Decrease (Increase) in accrued unbilled revenues			(4,889)	(32,053)
Decrease (increase) in fuel oil stock			43,974	(35,893)
Increase in materials and supplies			(7,139)	(7,599)
Increase in regulatory assets			(37,586)	(35,476)
Increase (decrease) in accounts payable			(41,234)	5,931
Changes in prepaid and accrued income taxes and revenue taxes			(38,123)	(21,141)
Contributions to defined benefit pension and other postretirement benefit plans			(40,586)	(52,086)
Other increase in defined benefit pension and other postretirement benefit plans liability			41,575	31,166
Change in other assets and liabilities			(9,394)	(37,917)
Net cash provided by (used in) operating activities			111,702	(21,525)
Cash flows from investing activities
Capital expenditures			(150,251)	(141,618)
Contributions in aid of construction			17,188	26,981
Other			623
Net cash used in investing activities			(132,440)	(114,637)
Cash flows from financing activities
Common stock dividends			(40,789)	(36,522)
Preferred stock dividends of HECO and subsidiaries			(998)	(998)
Proceeds from issuance of long-term debt				417,000
Repayment of long-term debt				(328,500)
Net increase in short-term borrowings from nonaffiliates and affiliate with original maturities of three months or less			53,992	44,242
Other			(9)	(1,929)
Net cash provided by financing activities			12,196	93,293
Net decrease in cash and cash equivalents			(8,542)	(42,869)
Cash and cash equivalents, beginning of period			17,159	48,806
Cash and cash equivalents, end of period	$ 8,617	$ 5,937	$ 8,617	$ 5,937