Consolidating financial information (Details 5) - HECO (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities
Net income	$ 39,273	$ 27,612	$ 78,062	$ 56,547
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation of property, plant and equipment			75,517	75,243
Other amortization			2,999	11,965
Change in deferred income taxes			41,541	39,051
Allowance for equity funds used during construction	(1,997)	(1,317)	(3,937)	(2,561)
Change in cash overdraft				(2,305)
Changes in assets and liabilities
Decrease (increase) in fuel oil stock			(35,893)	(6,509)
Change in prepaid and accrued income taxes and utility revenue taxes			(12,998)	8,333
Contributions to defined benefit pension and other postretirement benefit plans			(53,356)	(37,556)
Change in other assets and liabilities			(62,910)	(7,352)
Net cash provided by (used in) operating activities			(3,572)	55,181
Cash flows from investing activities
Capital expenditures			(145,263)	(89,088)
Contributions in aid of construction			26,981	8,153
Other				(2,911)
Net cash used in investing activities			(188,313)	(214,220)
Cash flows from financing activities
Common stock dividends			(47,851)	(47,331)
Proceeds from issuance of long-term debt			417,000	125,000
Repayment of long-term debt			(328,500)	(50,000)
Net increase (decrease) in short-term borrowings with original maturities of three months or less			27,419	(24,923)
Other			(2,055)	(172)
Net cash provided by financing activities			129,169	95,134
Net increase (decrease) in cash and cash equivalents			(62,716)	(63,905)
HECO
Cash flows from operating activities
Net income	29,646	17,294	57,216	36,753
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in earnings of subsidiaries			(16,790)	(22,503)
Common stock dividends received from subsidiaries			10,967	14,113
Depreciation of property, plant and equipment			45,308	45,768
Other amortization			347	8,602
Change in deferred income taxes			31,673	19,474
Change in tax credits, net			2,641	1,193
Allowance for equity funds used during construction	(1,654)	(974)	(3,235)	(1,934)
Changes in assets and liabilities
Increase in accounts receivable			(17,653)	(25,879)
Increase in accrued unbilled revenues			(21,274)	(16,571)
Decrease (increase) in fuel oil stock			(28,905)	12,090
Increase in materials and supplies			(6,172)	(956)
Increase in regulatory assets			(28,190)	(9,650)
Increase (decrease) in accounts payable			12,843	(45,638)
Change in prepaid and accrued income taxes and utility revenue taxes			(9,994)	3,724
Contributions to defined benefit pension and other postretirement benefit plans			(38,693)	(27,431)
Change in other assets and liabilities			(4,021)	9,116
Net cash provided by (used in) operating activities			(13,932)	271
Cash flows from investing activities
Capital expenditures			(111,011)	(60,386)
Contributions in aid of construction			23,693	4,816
Other				77
Investment in consolidated subsidiary				(25)
Advances from (to) affiliates			(8,700)
Net cash used in investing activities			(96,018)	(55,518)
Cash flows from financing activities
Common stock dividends			(36,522)	(35,279)
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 (decrease) in short-term borrowings with original maturities of three months or less			(1,058)	(6,650)
Other			(1,746)	(16)
Net cash provided by financing activities			67,554	(42,485)
Net increase (decrease) in cash and cash equivalents			(42,396)	(97,732)
Cash and cash equivalents, beginning of period			44,819	121,019
Cash and cash equivalents, end of period	2,423	23,287	2,423	23,287
HELCO
Cash flows from operating activities
Net income	4,624	6,708	11,369	13,459
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation of property, plant and equipment			16,737	16,471
Other amortization			1,418	1,283
Change in deferred income taxes			5,857	6,234
Change in tax credits, net			125	307
Allowance for equity funds used during construction	(160)	(233)	(285)	(316)
Change in cash overdraft				(2,527)
Changes in assets and liabilities
Increase in accounts receivable			(137)	(3,111)
Increase in accrued unbilled revenues			(6,456)	(1,769)
Decrease (increase) in fuel oil stock			(514)	(5,168)
Increase in materials and supplies			(1,022)	(88)
Increase in regulatory assets			(3,234)	(1,057)
Increase (decrease) in accounts payable			(6,938)	(35)
Change in prepaid and accrued income taxes and utility revenue taxes			(6,347)	3,682
Contributions to defined benefit pension and other postretirement benefit plans			(6,536)	(4,638)
Change in other assets and liabilities			657	3,502
Net cash provided by (used in) operating activities			4,694	26,229
Cash flows from investing activities
Capital expenditures			(17,405)	(13,937)
Contributions in aid of construction			2,327	2,501
Advances from (to) affiliates			26,800	(5,850)
Net cash used in investing activities			11,722	(17,286)
Cash flows from financing activities
Common stock dividends			(6,569)	(8,061)
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			171
Net cash provided by financing activities			(16,865)	(8,328)
Net increase (decrease) in cash and cash equivalents			(449)	615
Cash and cash equivalents, beginning of period			3,383	1,229
Cash and cash equivalents, end of period	2,934	1,844	2,934	1,844
MECO
Cash flows from operating activities
Net income	3,856	4,485	5,831	9,458
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation of property, plant and equipment			10,570	10,451
Other amortization			1,005	948
Change in deferred income taxes			4,994	7,748
Change in tax credits, net			114	56
Allowance for equity funds used during construction	(183)	(110)	(417)	(311)
Change in cash overdraft				222
Changes in assets and liabilities
Increase in accounts receivable			(702)	(5,486)
Increase in accrued unbilled revenues			(4,323)	(139)
Decrease (increase) in fuel oil stock			(6,474)	(13,431)
Increase in materials and supplies			(405)	(446)
Increase in regulatory assets			(4,052)	(3,791)
Increase (decrease) in accounts payable			26	(2,615)
Change in prepaid and accrued income taxes and utility revenue taxes			(4,800)	4,772
Contributions to defined benefit pension and other postretirement benefit plans			(6,857)	(4,952)
Change in other assets and liabilities			4,148	1,143
Net cash provided by (used in) operating activities			(1,342)	3,627
Cash flows from investing activities
Capital expenditures			(13,202)	(11,072)
Contributions in aid of construction			961	836
Advances from (to) affiliates			18,500	12,500
Net cash used in investing activities			6,259	2,264
Cash flows from financing activities
Common stock dividends			(4,373)	(6,002)
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 (decrease) in short-term borrowings with original maturities of three months or less			8,700
Other			(354)	(1)
Net cash provided by financing activities			(4,938)	(6,194)
Net increase (decrease) in cash and cash equivalents			(21)	(303)
Cash and cash equivalents, beginning of period			496	594
Cash and cash equivalents, end of period	475	291	475	291
RHI
Cash flows from operating activities
Net income			(1)	(2)
Changes in assets and liabilities
Change in other assets and liabilities			(1)	(2)
Net cash provided by (used in) operating activities			(2)	(4)
Cash flows from financing activities
Net increase (decrease) in cash and cash equivalents			(2)	(4)
Cash and cash equivalents, beginning of period			82	89
Cash and cash equivalents, end of period	80	85	80	85
UBC
Cash flows from operating activities
Net income	(1)	(1)	(1)	(4)
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
Other				25
Net cash provided by financing activities				25
Net increase (decrease) in cash and cash equivalents			(1)	22
Cash and cash equivalents, beginning of period			26	5
Cash and cash equivalents, end of period	25	27	25	27
Elimination addition to (deduction from) cash flows
Cash flows from operating activities
Net income	(8,250)	(10,963)	(16,740)	(22,453)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in earnings of subsidiaries			16,740	22,453
Common stock dividends received from subsidiaries			(10,942)	(14,063)
Changes in assets and liabilities
Increase in accounts receivable			7,534	1,164
Change in other assets and liabilities			(7,534)	(1,164)
Net cash provided by (used in) operating activities			(10,942)	(14,063)
Cash flows from investing activities
Investment in consolidated subsidiary				25
Advances from (to) affiliates			(36,600)	(6,650)
Net cash used in investing activities			(36,600)	(6,625)
Cash flows from financing activities
Common stock dividends			10,942	14,063
Net increase (decrease) in short-term borrowings with original maturities of three months or less			36,600	6,650
Other				(25)
Net cash provided by financing activities			47,542	20,688
HECO Consolidated
Cash flows from operating activities
Net income	29,875	17,523	57,674	37,211
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in earnings of subsidiaries			(50)	(50)
Common stock dividends received from subsidiaries			25	50
Depreciation of property, plant and equipment			72,615	72,690
Other amortization			2,770	10,833
Change in deferred income taxes			42,524	33,456
Change in tax credits, net			2,880	1,556
Allowance for equity funds used during construction	(1,997)	(1,317)	(3,937)	(2,561)
Change in cash overdraft				(2,305)
Changes in assets and liabilities
Increase in accounts receivable			(10,958)	(33,312)
Increase in accrued unbilled revenues			(32,053)	(18,479)
Decrease (increase) in fuel oil stock			(35,893)	(6,509)
Increase in materials and supplies			(7,599)	(1,490)
Increase in regulatory assets			(35,476)	(14,498)
Increase (decrease) in accounts payable			5,931	(48,288)
Change in prepaid and accrued income taxes and utility revenue taxes			(21,141)	12,178
Contributions to defined benefit pension and other postretirement benefit plans			(52,086)	(37,021)
Change in other assets and liabilities			(6,776)	12,596
Net cash provided by (used in) operating activities			(21,525)	16,057
Cash flows from investing activities
Capital expenditures			(141,618)	(85,395)
Contributions in aid of construction			26,981	8,153
Other				77
Net cash used in investing activities			(114,637)	(77,165)
Cash flows from financing activities
Common stock dividends			(36,522)	(35,279)
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 (decrease) in short-term borrowings with original maturities of three months or less			44,242
Other			(1,929)	(17)
Net cash provided by financing activities			93,293	(36,294)
Net increase (decrease) in cash and cash equivalents			(42,869)	(97,402)
Cash and cash equivalents, beginning of period			48,806	122,936
Cash and cash equivalents, end of period	$ 5,937	$ 25,534	$ 5,937	$ 25,534