Electric utility segment Consolidating Statement of Cash Flows (Details) - USD ($) $ in Thousands		3 Months Ended									12 Months Ended
		Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012
Cash flows from operating activities
Net income (loss)		$ 33,630	$ 48,286	$ 41,894	$ 46,400	$ 39,486		$ 48,707	$ 41,061	$ 34,152	$ 170,210	$ 163,406	[1]	$ 140,548	[1]
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment											172,762	160,061	[1]	150,389	[1]
Other amortization											6,795	4,667	[1]	7,958	[1]
Impairment of utility plant											0	0	[1]	40,000	[1]
Increase (decrease) in deferred income taxes											103,916	80,399	[1]	90,848	[1]
Allowance for equity funds used during construction											(6,771)	(5,561)	[1]	(7,007)	[1]
Change in cash overdraft											(1,038)	1,038	[1]	0	[1]
Decrease (increase) in fuel oil stock											28,041	27,332	[1]	10,129	[1]
Increase in regulatory assets											(17,000)	(65,461)	[1]	(72,401)	[1]
Change in prepaid and accrued income taxes and utility revenue taxes											(39,091)	(19,406)	[1]	21,079	[1]
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability											22,251	(33,014)	[1]	(228)	[1]
Net cash provided by operating activities											325,420	361,568	[1]	278,934	[1]
Cash flows from investing activities
Capital expenditures											(364,826)	(389,438)	[1]	(370,715)	[1]
Contributions in aid of construction											41,806	32,160	[1]	45,982	[1]
Other											1,125	1,177	[1]	1,778	[1]
Net cash used in investing activities											(592,449)	(598,182)	[1]	(471,439)	[1]
Cash flows from financing activities
Common stock dividends											(126,458)	(98,383)	[1]	(96,202)	[1]
Proceeds from issuance of long-term debt											125,000	286,000	[1]	457,000	[1]
Proceeds from issuance of common stock											26,898	55,086	[1]	23,613	[1]
Repayment of long-term debt											(111,400)	(216,000)	[1]	(375,500)	[1]
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less											13,490	21,789	[1]	14,872	[1]
Other											(456)	(1,187)	[1]	(2,645)	[1]
Net cash provided by (used in) financing activities											222,535	236,988	[1]	141,902	[1]
Net increase (decrease) in cash and cash equivalents											(44,494)	374	[1]	(50,603)	[1]
As previously filed
Adjustments to reconcile net income to net cash provided by operating activities
Other amortization											8,476
Increase (decrease) in deferred income taxes											59,184
Change in prepaid and accrued income taxes and utility revenue taxes											12,845
Net cash provided by operating activities											301,479	327,146		234,542
Cash flows from investing activities
Capital expenditures											(339,721)	(353,879)		(325,480)
Other											(39)	40		935
Net cash used in investing activities											(568,508)	(563,760)		(427,047)
HECO
Cash flows from operating activities
Net income (loss)											138,721	124,009		100,356
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings											(41,064)	(41,510)		(28,936)
Common stock dividends received from subsidiaries											26,076	28,505		47,035
Depreciation of property, plant and equipment											109,204	99,738		90,783
Other amortization											1,749	554		1,508
Impairment of utility plant														29,000
Increase (decrease) in deferred income taxes											56,901	41,409		66,968
Change in tax credits, net											4,998	5,152		5,006
Allowance for equity funds used during construction											(6,085)	(4,495)		(5,735)
Decrease (increase) in accounts receivable											16,213	49,974		(48,451)
Decrease (increase) in accrued unbilled revenues											4,680	(7,152)		2,728
Decrease (increase) in fuel oil stock											25,098	23,563		4,861
Increase in materials and supplies											4,223	(5,598)		(6,683)
Increase in regulatory assets											(14,620)	(46,047)		(55,605)
Increase (decrease) in accounts payable											(56,044)	18,527		6,329
Change in prepaid and accrued income taxes and utility revenue taxes											(4,166)	4,632		19,871
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability											(562)	2,325		(434)
Changes in other assets and liabilities											(46,636)	(18,618)		(45,366)
Net cash provided by operating activities											218,686	274,968		183,235
Cash flows from investing activities
Capital expenditures											(237,970)	(262,562)		(271,864)
Contributions in aid of construction											30,021	21,686		32,285
Advances from affiliates											(9,261)	2,561		(9,400)
Other											604	677		486
Investment in consolidated subsidiary											0	(12,461)
Net cash used in investing activities											(216,606)	(250,099)		(248,493)
Cash flows from financing activities
Common stock dividends											(88,492)	(81,578)		(73,044)
Preferred stock dividends of Hawaiian Electric and subsidiaries											(1,080)	(1,080)		(1,080)
Proceeds from issuance of long-term debt											0	140,000		367,000
Proceeds from issuance of common stock											40,000	78,500		44,000
Repayment of long-term debt											0	(90,000)		(259,580)
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less											(1,000)	(17,050)		(46,600)
Other											(337)	(681)		(1,992)
Net cash provided by (used in) financing activities											(50,909)	28,111		28,704
Net increase (decrease) in cash and cash equivalents											(48,829)	52,980		(36,554)
Cash and cash equivalents, January 1					61,245					8,265	61,245	8,265		44,819
Cash and cash equivalents, December 31		12,416				61,245					12,416	61,245		8,265
HECO | As previously filed
Adjustments to reconcile net income to net cash provided by operating activities
Increase (decrease) in accounts payable											(74,276)	(6,136)		(31,743)
Changes in other assets and liabilities											(46,032)	(17,941)		(44,880)
Cash flows from investing activities
Capital expenditures											(219,738)	(237,899)		(233,792)
Other											0	0		0
HELCO
Cash flows from operating activities
Net income (loss)											19,223	20,670		16,746
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment											35,904	34,188		33,337
Other amortization											2,596	1,979		3,252
Impairment of utility plant														5,500
Increase (decrease) in deferred income taxes											12,083	10,569		7,457
Change in tax credits, net											680	818		522
Allowance for equity funds used during construction											(472)	(643)		(585)
Decrease (increase) in accounts receivable											7,150	(1,459)		(1,106)
Decrease (increase) in accrued unbilled revenues											1,174	(2,707)		4,106
Decrease (increase) in fuel oil stock											378	1,307		3,732
Increase in materials and supplies											219	(1,547)		(636)
Increase in regulatory assets											(3,357)	(9,237)		(9,649)
Increase (decrease) in accounts payable											(6,645)	1,525		(5,774)
Change in prepaid and accrued income taxes and utility revenue taxes											(3,251)	(4,114)		1,935
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability											0	(1)		(191)
Changes in other assets and liabilities											(12,577)	(6,513)		(11,335)
Net cash provided by operating activities											53,105	44,835		47,311
Cash flows from investing activities
Capital expenditures											(49,895)	(58,416)		(43,396)
Contributions in aid of construction											7,695	7,590		8,184
Advances from affiliates											1,000	17,050		28,100
Other											492	21		192
Net cash used in investing activities											(40,708)	(33,755)		(6,920)
Cash flows from financing activities
Common stock dividends											(11,627)	(14,388)		(27,738)
Preferred stock dividends of Hawaiian Electric and subsidiaries											(534)	(534)		(534)
Proceeds from issuance of long-term debt											0	56,000		31,000
Proceeds from issuance of common stock														0
Repayment of long-term debt											(11,400)	(56,000)		(41,200)
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less											10,500			0
Other											(50)	(273)		139
Net cash provided by (used in) financing activities											(13,111)	(15,195)		(38,333)
Net increase (decrease) in cash and cash equivalents											(714)	(4,115)		2,058
Cash and cash equivalents, January 1					1,326					5,441	1,326	5,441		3,383
Cash and cash equivalents, December 31		612				1,326					612	1,326		5,441
HELCO | As previously filed
Adjustments to reconcile net income to net cash provided by operating activities
Increase (decrease) in accounts payable											(8,490)	(4,756)		(8,110)
Changes in other assets and liabilities											(12,085)	(6,262)		(11,143)
Cash flows from investing activities
Capital expenditures											(48,050)	(52,135)		(41,060)
Other											0	(230)		0
MECO
Cash flows from operating activities
Net income (loss)											22,656	21,658		13,008
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment											21,279	20,099		20,378
Other amortization											2,065	2,544		2,238
Impairment of utility plant														5,500
Increase (decrease) in deferred income taxes											13,963	12,529		12,453
Change in tax credits, net											384	1,047		547
Allowance for equity funds used during construction											(214)	(423)		(687)
Change in cash overdraft											(1,038)	1,038
Decrease (increase) in accounts receivable											3,483	1,178		(2,164)
Decrease (increase) in accrued unbilled revenues											896	33		(3,306)
Decrease (increase) in fuel oil stock											2,565	2,462		1,536
Increase in materials and supplies											(2,648)	(814)		(578)
Increase in regulatory assets											977	(10,177)		(7,147)
Increase (decrease) in accounts payable											(2,838)	(5,321)		5,767
Change in prepaid and accrued income taxes and utility revenue taxes											3,381	(2,546)		3,433
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability											(399)	(84)		(119)
Changes in other assets and liabilities											(3,332)	(7,753)		(12,843)
Net cash provided by operating activities											61,180	35,470		38,016
Cash flows from investing activities
Capital expenditures											(48,814)	(57,066)		(40,066)
Contributions in aid of construction											4,090	2,884		5,513
Advances from affiliates											0	0		18,500
Other											68	209		165
Net cash used in investing activities											(44,656)	(53,973)		(15,888)
Cash flows from financing activities
Common stock dividends											(14,349)	(14,017)		(19,197)
Preferred stock dividends of Hawaiian Electric and subsidiaries											(381)	(381)		(381)
Proceeds from issuance of long-term debt											0	40,000		59,000
Proceeds from issuance of common stock											0	12,461		0
Repayment of long-term debt											0	(20,000)		(67,720)
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less											(1,239)	(2,561)		9,400
Other											(75)	(195)		(377)
Net cash provided by (used in) financing activities											(16,044)	15,307		(19,275)
Net increase (decrease) in cash and cash equivalents											480	(3,196)		2,853
Cash and cash equivalents, January 1					153					3,349	153	3,349		496
Cash and cash equivalents, December 31		633				153					633	153		3,349
MECO | As previously filed
Adjustments to reconcile net income to net cash provided by operating activities
Other amortization											3,746
Increase (decrease) in accounts payable											(7,866)	(9,936)		940
Changes in other assets and liabilities											(4,945)	(7,544)		(12,678)
Cash flows from investing activities
Capital expenditures											(43,786)	(52,451)		(35,239)
Other											0	0		0
Other subsidiaries
Cash flows from operating activities
Net income (loss)											0	(3)		(3)
Adjustments to reconcile net income to net cash provided by operating activities
Changes in other assets and liabilities											0	0		(1)
Net cash provided by operating activities											0	(3)		(4)
Cash flows from financing activities
Proceeds from issuance of common stock														0
Net cash provided by (used in) financing activities														0
Net increase (decrease) in cash and cash equivalents											0	(3)		(4)
Cash and cash equivalents, January 1					101					104	101	104		108
Cash and cash equivalents, December 31		101				101					101	101		104
Other subsidiaries | As previously filed
Adjustments to reconcile net income to net cash provided by operating activities
Changes in other assets and liabilities														(1)
Consolidating adjustments
Cash flows from operating activities
Net income (loss)											(40,964)	(41,410)		(28,836)
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings											40,964	41,410		28,836
Common stock dividends received from subsidiaries											(25,976)	(28,405)		(46,935)
Decrease (increase) in accounts receivable											(103)	(248)		4,717
Changes in other assets and liabilities											103	248		(4,717)
Net cash provided by operating activities											(25,976)	(28,405)		(46,935)
Cash flows from investing activities
Advances from affiliates											8,261	(19,611)		(37,200)
Other											0
Investment in consolidated subsidiary											0	12,461
Net cash used in investing activities											8,261	(7,150)		(37,200)
Cash flows from financing activities
Common stock dividends											25,976	28,405		46,935
Proceeds from issuance of common stock											0	(12,461)		0
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less											(8,261)	19,611		37,200
Net cash provided by (used in) financing activities											17,715	35,555		84,135
Consolidating adjustments | As previously filed
Adjustments to reconcile net income to net cash provided by operating activities
Changes in other assets and liabilities											103	248		(4,717)
HECO Consolidated
Cash flows from operating activities
Net income (loss)		29,611	$ 39,377	$ 34,729	35,919	32,489		$ 38,315	$ 29,192	24,928	139,636	124,924	[1]	101,271	[1]
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings											(100)	(100)		(100)
Common stock dividends received from subsidiaries											100	100		100
Depreciation of property, plant and equipment											166,387	154,025	[1]	144,498	[1]
Other amortization											6,410	5,077	[1]	6,998	[1]
Impairment of utility plant											0	0	[1]	40,000	[1]
Increase (decrease) in deferred income taxes											82,947	64,507	[1]	86,878	[1]
Change in tax credits, net											6,062	7,017	[1]	6,075	[1]
Allowance for equity funds used during construction											(6,771)	(5,561)	[1]	(7,007)	[1]
Change in cash overdraft											(1,038)	1,038	[1]	0	[1]
Decrease (increase) in accounts receivable											26,743	49,445	[1]	(47,004)	[1]
Decrease (increase) in accrued unbilled revenues											6,750	(9,826)	[1]	3,528	[1]
Decrease (increase) in fuel oil stock											28,041	27,332	[1]	10,129	[1]
Increase in materials and supplies											1,794	(7,959)	[1]	(7,897)	[1]
Increase in regulatory assets											(17,000)	(65,461)	[1]	(72,401)	[1]
Increase (decrease) in accounts payable											(65,527)	14,731	[1]	6,322	[1]
Change in prepaid and accrued income taxes and utility revenue taxes											(4,036)	(2,028)	[1]	25,239	[1]
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability											(961)	2,240	[1]	(744)	[1]
Changes in other assets and liabilities											(62,442)	(32,636)		(74,262)
Net cash provided by operating activities											306,995	326,865	[1]	221,623	[1]
Cash flows from investing activities
Capital expenditures											(336,679)	(378,044)	[1]	(355,326)	[1]
Contributions in aid of construction											41,806	32,160	[1]	45,982	[1]
Other											1,164	907	[1]	843	[1]
Net cash used in investing activities											(293,709)	(344,977)	[1]	(308,501)	[1]
Cash flows from financing activities
Common stock dividends											(88,492)	(81,578)	[1]	(73,044)	[1]
Preferred stock dividends of Hawaiian Electric and subsidiaries											(1,995)	(1,995)	[1]	(1,995)	[1]
Proceeds from issuance of long-term debt											0	236,000	[1]	457,000	[1]
Proceeds from issuance of common stock											40,000	78,500	[1]	44,000	[1]
Repayment of long-term debt											(11,400)	(166,000)	[1]	(368,500)	[1]
Other											(462)	(1,149)	[1]	(2,230)	[1]
Net cash provided by (used in) financing activities											(62,349)	63,778	[1]	55,231	[1]
Net increase (decrease) in cash and cash equivalents											(49,063)	45,666	[1]	(31,647)	[1]
Cash and cash equivalents, January 1	[1]				$ 62,825					$ 17,159	62,825	17,159		48,806
Cash and cash equivalents, December 31		$ 13,762				$ 62,825	[1]				13,762	62,825	[1]	17,159	[1]
HECO Consolidated | As previously filed
Adjustments to reconcile net income to net cash provided by operating activities
Other amortization											8,091
Increase (decrease) in accounts payable											(90,632)	(20,828)		(38,913)
Changes in other assets and liabilities											(62,959)	(31,499)		(73,419)
Net cash provided by operating activities											283,054	292,443		177,231
Cash flows from investing activities
Capital expenditures											(311,574)	(342,485)		(310,091)
Other											0	(230)		0
Net cash used in investing activities											$ (269,768)	$ (310,555)		$ (264,109)

[1] As restated - See Note 1, “Summary of significant accounting policies - Revision and restatements of previously issued financial statements.”