Consolidating financial information (Details 5) - HECO (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities
Net income (loss)	$ 48,707	$ 48,177	$ 123,920	$ 126,239
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation of property, plant and equipment			120,355	112,946
Other amortization			2,352	4,811
Change in deferred income taxes			60,580	82,582
Allowance for equity funds used during construction	(1,255)	(1,611)	(4,030)	(5,548)
Changes in assets and liabilities
Decrease in fuel oil stock			24,332	(31,372)
Increase in regulatory assets			(53,314)	(57,793)
Changes in prepaid and accrued income taxes and revenue taxes			(19,212)	(5,121)
Contributions to defined benefit pension and other postretirement benefit plans			(62,279)	(64,006)
Other increase in defined benefit pension and other postretirement benefit plans liability			61,770	49,950
Net cash provided by (used in) operating activities			246,726	121,604
Cash flows from investing activities
Capital expenditures			(247,392)	(225,961)
Contributions in aid of construction			23,633	33,106
Other			3,035	865
Net cash used in investing activities			(363,424)	(297,249)
Cash flows from financing activities
Common stock dividends			(73,584)	(71,966)
Proceeds from issuance of long-term debt			50,000	457,000
Repayment of long-term debt			(50,000)	(368,500)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			47,648	13,398
Other			(4,033)	(6,314)
Net cash provided by (used in) financing activities			112,078	73,892
Net decrease in cash and cash equivalents			(4,620)	(101,753)
HECO
Cash flows from operating activities
Net income (loss)	38,087	38,645	91,749	95,861
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in earnings			(30,522)	(28,100)
Common stock dividends received from subsidiaries			21,379	16,464
Depreciation of property, plant and equipment			75,150	68,046
Other amortization			(228)	691
Change in deferred income taxes			31,361	64,790
Changes in tax credits, net			3,773	3,256
Allowance for equity funds used during construction	(914)	(1,323)	(3,144)	(4,558)
Changes in assets and liabilities
Decrease (increase) in accounts receivable			37,894	(43,284)
Decrease (Increase) in accrued unbilled revenues			(4,381)	3,427
Decrease in fuel oil stock			17,945	(36,365)
Increase in materials and supplies			(5,392)	(6,320)
Increase in regulatory assets			(37,032)	(44,175)
Decrease in accounts payable			(10,435)	7,872
Changes in prepaid and accrued income taxes and revenue taxes			(7,122)	(14,006)
Contributions to defined benefit pension and other postretirement benefit plans			(44,650)	(45,878)
Other increase in defined benefit pension and other postretirement benefit plans liability			46,394	34,421
Change in other assets and liabilities			(10,562)	(28,970)
Net cash provided by (used in) operating activities			172,177	43,172
Cash flows from investing activities
Capital expenditures			(164,423)	(172,872)
Contributions in aid of construction			15,699	25,547
Other			623
Advances from (to) affiliates			(13,600)	0
Net cash used in investing activities			(161,701)	(147,325)
Cash flows from financing activities
Common stock dividends			(61,183)	(54,783)
Preferred stock dividends of HECO and subsidiaries			(810)	(810)
Proceeds from issuance of long-term debt				367,000
Repayment of long-term debt				(259,580)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			62,196	16,469
Other			(38)	(1,980)
Net cash provided by (used in) financing activities			165	66,316
Net decrease in cash and cash equivalents			10,641	(37,837)
Cash and cash equivalents, beginning of period			8,265	44,819
Cash and cash equivalents, end of period	18,906	6,982	18,906	6,982
HELCO
Cash flows from operating activities
Net income (loss)	5,577	4,861	15,144	16,230
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation of property, plant and equipment			25,641	25,036
Other amortization			1,075	1,776
Change in deferred income taxes			7,165	8,290
Changes in tax credits, net			119	256
Allowance for equity funds used during construction	(222)	(148)	(552)	(433)
Changes in assets and liabilities
Decrease (increase) in accounts receivable			(2,552)	(7,236)
Decrease (Increase) in accrued unbilled revenues			(1,727)	3,107
Decrease in fuel oil stock			870	3,163
Increase in materials and supplies			(1,706)	(719)
Increase in regulatory assets			(7,165)	(6,621)
Decrease in accounts payable			(3,343)	(8,518)
Changes in prepaid and accrued income taxes and revenue taxes			(3,566)	(3,562)
Contributions to defined benefit pension and other postretirement benefit plans			(8,083)	(8,270)
Other increase in defined benefit pension and other postretirement benefit plans liability			7,892	6,133
Change in other assets and liabilities			(1,821)	(1,120)
Net cash provided by (used in) operating activities			27,391	27,512
Cash flows from investing activities
Capital expenditures			(35,900)	(26,331)
Contributions in aid of construction			6,160	4,199
Other			(196)
Advances from (to) affiliates			11,050	16,750
Net cash used in investing activities			(18,886)	(5,382)
Cash flows from financing activities
Common stock dividends			(10,790)	(9,854)
Preferred stock dividends of HECO and subsidiaries			(400)	(400)
Proceeds from issuance of long-term debt				31,000
Repayment of long-term debt				(41,200)
Other			(2)	167
Net cash provided by (used in) financing activities			(11,192)	(20,287)
Net decrease in cash and cash equivalents			(2,687)	1,843
Cash and cash equivalents, beginning of period			5,441	3,383
Cash and cash equivalents, end of period	2,754	5,226	2,754	5,226
MECO
Cash flows from operating activities
Net income (loss)	5,446	6,653	15,990	12,484
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation of property, plant and equipment			15,074	15,474
Other amortization			1,623	1,607
Change in deferred income taxes			9,488	9,637
Changes in tax credits, net			618	130
Allowance for equity funds used during construction	(119)	(140)	(334)	(557)
Changes in assets and liabilities
Decrease (increase) in accounts receivable			3,999	1,287
Decrease (Increase) in accrued unbilled revenues			505	(798)
Decrease in fuel oil stock			5,517	1,830
Increase in materials and supplies			(1,251)	(266)
Increase in regulatory assets			(9,117)	(6,997)
Decrease in accounts payable			(9,196)	(2,835)
Changes in prepaid and accrued income taxes and revenue taxes			(4,728)	(3,097)
Contributions to defined benefit pension and other postretirement benefit plans			(8,143)	(8,269)
Other increase in defined benefit pension and other postretirement benefit plans liability			8,078	9,307
Change in other assets and liabilities			4,924	(3,192)
Net cash provided by (used in) operating activities			33,047	25,745
Cash flows from investing activities
Capital expenditures			(37,546)	(21,767)
Contributions in aid of construction			1,774	3,360
Advances from (to) affiliates				11,500
Net cash used in investing activities			(35,772)	(6,907)
Cash flows from financing activities
Common stock dividends			(10,513)	(6,560)
Preferred stock dividends of HECO and subsidiaries			(286)	(286)
Proceeds from issuance of long-term debt				59,000
Repayment of long-term debt				(67,720)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			13,600	0
Other			(2)	(359)
Net cash provided by (used in) financing activities			2,799	(15,925)
Net decrease in cash and cash equivalents			74	2,913
Cash and cash equivalents, beginning of period			3,349	496
Cash and cash equivalents, end of period	3,423	3,409	3,423	3,409
Other subsidiaries
Cash flows from operating activities
Net income (loss)	(1)	(1)	(2)	(3)
Changes in assets and liabilities
Change in other assets and liabilities				0
Net cash provided by (used in) operating activities			(2)	(3)
Cash flows from financing activities
Net decrease in cash and cash equivalents			(2)	(3)
Cash and cash equivalents, beginning of period			104	108
Cash and cash equivalents, end of period	102	105	102	105
Consolidating adjustments
Cash flows from operating activities
Net income (loss)	(10,794)	(11,285)	(30,446)	(28,025)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in earnings			30,446	28,025
Common stock dividends received from subsidiaries			(21,303)	(16,414)
Changes in assets and liabilities
Decrease (increase) in accounts receivable			2,736	12,326
Change in other assets and liabilities			(2,736)	(12,326)
Net cash provided by (used in) operating activities			(21,303)	(16,414)
Cash flows from investing activities
Advances from (to) affiliates			2,550	(28,250)
Net cash used in investing activities			2,550	(28,250)
Cash flows from financing activities
Common stock dividends			21,303	16,414
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			(2,550)	28,250
Net cash provided by (used in) financing activities			18,753	44,664
HECO Consolidated
Cash flows from operating activities
Net income (loss)	38,315	38,873	92,435	96,547
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in earnings			(76)	(75)
Common stock dividends received from subsidiaries			76	50
Depreciation of property, plant and equipment			115,865	108,556
Other amortization			2,470	4,074
Change in deferred income taxes			48,014	82,717
Changes in tax credits, net			4,510	3,642
Allowance for equity funds used during construction	(1,255)	(1,611)	(4,030)	(5,548)
Changes in assets and liabilities
Decrease (increase) in accounts receivable			42,077	(36,907)
Decrease (Increase) in accrued unbilled revenues			(5,603)	5,736
Decrease in fuel oil stock			24,332	(31,372)
Increase in materials and supplies			(8,349)	(7,305)
Increase in regulatory assets			(53,314)	(57,793)
Decrease in accounts payable			(22,974)	(3,481)
Changes in prepaid and accrued income taxes and revenue taxes			(15,416)	(20,665)
Contributions to defined benefit pension and other postretirement benefit plans			(60,876)	(62,417)
Other increase in defined benefit pension and other postretirement benefit plans liability			62,364	49,861
Change in other assets and liabilities			(10,195)	(45,608)
Net cash provided by (used in) operating activities			211,310	80,012
Cash flows from investing activities
Capital expenditures			(237,869)	(220,970)
Contributions in aid of construction			23,633	33,106
Other			427	0
Net cash used in investing activities			(213,809)	(187,864)
Cash flows from financing activities
Common stock dividends			(61,183)	(54,783)
Preferred stock dividends of HECO and subsidiaries			(1,496)	(1,496)
Proceeds from issuance of long-term debt			0	457,000
Repayment of long-term debt			0	(368,500)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			73,246	44,719
Other			(42)	(2,172)
Net cash provided by (used in) financing activities			10,525	74,768
Net decrease in cash and cash equivalents			8,026	(33,084)
Cash and cash equivalents, beginning of period			17,159	48,806
Cash and cash equivalents, end of period	$ 25,185	$ 15,722	$ 25,185	$ 15,722