Electric utility segment - Consolidating Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net income (loss)	$ 45,107	$ 127,613	$ 44,601	$ 32,825	$ 42,793	$ 51,144	$ 35,491	$ 32,339	$ 250,146	$ 161,767	$ 170,019
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment									194,273	183,966	172,762
Other amortization									10,473	11,619	10,282
Deferred income taxes									47,118	41,432	104,225
Allowance for equity funds used during construction									(8,325)	(6,928)	(6,771)
Changes in assets and liabilities
Decrease in fuel oil stock									4,786	34,830	28,041
Increase in regulatory assets									(18,273)	(24,182)	(17,000)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability									1,587	852	22,251
Net cash provided by operating activities									495,254	355,880	325,420
Cash flows from investing activities
Capital expenditures									(330,043)	(363,804)	(364,826)
Contributions in aid of construction									30,100	40,239	41,806
Other									856	7,940	1,125
Net cash used in investing activities									(736,465)	(705,724)	(592,449)
Cash flows from financing activities
Common stock dividends									(117,274)	(131,765)	(126,458)
Proceeds from issuance of common stock									13,220	104,435	26,898
Proceeds from issuance of long-term debt									115,000	80,000	125,000
Repayment of long-term debt									(75,000)	0	(111,400)
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less									(103,063)	(15,909)	13,490
Other									(219)	(833)	(456)
Net cash used in financing activities									219,185	474,780	222,535
Net increase (decrease) in cash and equivalents									(22,026)	124,936	(44,494)
HECO
Cash flows from operating activities
Net income (loss)									143,397	136,794	138,721
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings									(42,491)	(43,020)	(41,064)
Common stock dividends received from subsidiaries									47,843	25,296	26,076
Depreciation of property, plant and equipment									126,086	117,682	109,204
Other amortization									2,979	4,678	4,535
Impairment of utility assets										4,573	1,866
Deferred income taxes									54,721	53,338	56,901
Change in tax credits, net									177	4,284	4,998
Allowance for equity funds used during construction									(6,659)	(5,641)	(6,085)
Change in cash overdraft											0
Other									(2,694)	4,403	758
Changes in assets and liabilities
Decrease in accounts receivable									10,175	15,652	16,213
Decrease (increase) in accrued unbilled revenues									(5,741)	29,733	4,680
Decrease in fuel oil stock									2,216	25,060	25,098
Decrease (increase) in materials and supplies									993	2,233	2,357
Increase in regulatory assets									(16,161)	(20,356)	(14,620)
Increase (decrease) in accounts payable									(10,247)	(42,751)	(56,044)
Change in prepaid and accrued income taxes, tax credits and revenue taxes									2,933	(50,382)	(4,166)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability									599	870	(562)
Changes in other assets and liabilities									(11,682)	(24,197)	(50,180)
Net cash provided by operating activities									296,444	238,249	218,686
Cash flows from investing activities
Capital expenditures									(236,425)	(267,621)	(237,970)
Contributions in aid of construction									23,611	35,955	30,021
Advances from (to) affiliates									0	16,100	(9,261)
Other									1,932	924	604
Net cash used in investing activities									(210,882)	(214,642)	(216,606)
Cash flows from financing activities
Common stock dividends									(93,599)	(90,405)	(88,492)
Preferred stock dividends of Hawaiian Electric and subsidiaries									(1,080)	(1,080)	(1,080)
Proceeds from issuance of common stock									24,000		40,000
Proceeds from issuance of long-term debt									40,000	50,000
Repayment of long-term debt											0
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less									(9,500)	23,000	(1,000)
Other									(276)	(1,257)	(337)
Net cash used in financing activities									(40,455)	(19,742)	(50,909)
Net increase (decrease) in cash and equivalents									45,107	3,865	(48,829)
Cash and cash equivalents, beginning of period				16,281				12,416	16,281	12,416	61,245
Cash and cash equivalents, end of period	61,388				16,281				61,388	16,281	12,416
Hawaii Electric Light Company, Inc. (HELCO)
Cash flows from operating activities
Net income (loss)									21,789	21,289	19,223
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment									37,797	37,250	35,904
Other amortization									1,817	2,124	2,926
Impairment of utility assets										724
Deferred income taxes									7,027	8,295	12,083
Change in tax credits, net									60	527	680
Allowance for equity funds used during construction									(765)	(604)	(472)
Change in cash overdraft											0
Other									(810)	(2,476)
Changes in assets and liabilities
Decrease in accounts receivable									(718)	3,420	7,150
Decrease (increase) in accrued unbilled revenues									(1,033)	4,593	1,174
Decrease in fuel oil stock									81	5,490	378
Decrease (increase) in materials and supplies									(515)	(201)	219
Increase in regulatory assets									(1,243)	(3,930)	(3,357)
Increase (decrease) in accounts payable									768	(6,425)	(6,645)
Change in prepaid and accrued income taxes, tax credits and revenue taxes									2,645	(6,166)	(3,251)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability									53	(161)	0
Changes in other assets and liabilities									(78)	(3,545)	(12,907)
Net cash provided by operating activities									66,875	60,204	53,105
Cash flows from investing activities
Capital expenditures									(51,344)	(48,645)	(49,895)
Contributions in aid of construction									3,412	2,160	7,695
Advances from (to) affiliates									12,000	(15,500)	1,000
Other									175	132	492
Net cash used in investing activities									(35,757)	(61,853)	(40,708)
Cash flows from financing activities
Common stock dividends									(22,507)	(10,021)	(11,627)
Preferred stock dividends of Hawaiian Electric and subsidiaries									(534)	(534)	(534)
Proceeds from issuance of common stock									0
Proceeds from issuance of long-term debt									0	25,000
Repayment of long-term debt											(11,400)
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less									0	(10,500)	10,500
Other									(10)	(226)	(50)
Net cash used in financing activities									(23,051)	3,719	(13,111)
Net increase (decrease) in cash and equivalents									8,067	2,070	(714)
Cash and cash equivalents, beginning of period				2,682				612	2,682	612	1,326
Cash and cash equivalents, end of period	10,749				2,682				10,749	2,682	612
MECO
Cash flows from operating activities
Net income (loss)									21,517	22,546	22,656
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment									23,178	22,448	21,279
Other amortization									2,139	2,137	2,436
Impairment of utility assets										724
Deferred income taxes									12,661	13,707	13,963
Change in tax credits, net									(6)	33	384
Allowance for equity funds used during construction									(901)	(683)	(214)
Change in cash overdraft											(1,038)
Other									(427)	(255)
Changes in assets and liabilities
Decrease in accounts receivable									1,776	4,617	3,483
Decrease (increase) in accrued unbilled revenues									(410)	5,767	896
Decrease in fuel oil stock									2,489	4,280	2,565
Decrease (increase) in materials and supplies									272	789	(2,648)
Increase in regulatory assets									(869)	104	977
Increase (decrease) in accounts payable									(1,135)	(5,379)	(2,838)
Change in prepaid and accrued income taxes, tax credits and revenue taxes									(3,478)	(6,548)	3,381
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability									(168)	416	(399)
Changes in other assets and liabilities									(2,272)	(4,554)	(3,703)
Net cash provided by operating activities									54,366	60,149	61,180
Cash flows from investing activities
Capital expenditures									(32,668)	(33,895)	(48,814)
Contributions in aid of construction									3,077	2,124	4,090
Advances from (to) affiliates									(2,500)	(7,500)	0
Other									31	84	68
Net cash used in investing activities									(32,060)	(39,187)	(44,656)
Cash flows from financing activities
Common stock dividends									(25,261)	(15,175)	(14,349)
Preferred stock dividends of Hawaiian Electric and subsidiaries									(381)	(381)	(381)
Proceeds from issuance of common stock									0		0
Proceeds from issuance of long-term debt									0	5,000
Repayment of long-term debt											0
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less									0	(5,600)	(1,239)
Other									(1)	(54)	(75)
Net cash used in financing activities									(25,643)	(16,210)	(16,044)
Net increase (decrease) in cash and equivalents									(3,337)	4,752	480
Cash and cash equivalents, beginning of period				5,385				633	5,385	633	153
Cash and cash equivalents, end of period	2,048				5,385				2,048	5,385	633
Other subsidiaries
Cash flows from operating activities
Net income (loss)									0	0	0
Changes in assets and liabilities
Changes in other assets and liabilities									0	0	0
Net cash provided by operating activities									0	0	0
Cash flows from financing activities
Proceeds from issuance of common stock											0
Net increase (decrease) in cash and equivalents									0	0	0
Cash and cash equivalents, beginning of period				101				101	101	101	101
Cash and cash equivalents, end of period	101				101				101	101	101
Consolidating adjustments
Cash flows from operating activities
Net income (loss)									(42,391)	(42,920)	(40,964)
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings									42,391	42,920	40,964
Common stock dividends received from subsidiaries									(47,768)	(25,196)	(25,976)
Deferred income taxes									(23)	286
Changes in assets and liabilities
Decrease in accounts receivable									(2,682)	38	(103)
Change in prepaid and accrued income taxes, tax credits and revenue taxes									23
Changes in other assets and liabilities									2,682	(324)	103
Net cash provided by operating activities									(47,768)	(25,196)	(25,976)
Cash flows from investing activities
Advances from (to) affiliates									(9,500)	6,900	8,261
Other									0	0
Net cash used in investing activities									(9,500)	6,900	8,261
Cash flows from financing activities
Common stock dividends									47,768	25,196	25,976
Proceeds from issuance of common stock									0		0
Proceeds from issuance of long-term debt									0	0
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less									9,500	(6,900)	(8,261)
Net cash used in financing activities									57,268	18,296	17,715
HECO Consolidated
Cash flows from operating activities
Net income (loss)	34,618	$ 47,472	$ 36,356	25,866	33,492	$ 43,504	$ 33,340	27,373	144,312	137,709	139,636
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings									(100)	(100)	(100)
Common stock dividends received from subsidiaries									75	100	100
Depreciation of property, plant and equipment									187,061	177,380	166,387
Other amortization									6,935	8,939	9,897
Impairment of utility assets										6,021	1,866
Deferred income taxes									74,386	75,626	82,947
Change in tax credits, net									231	4,844	6,062
Allowance for equity funds used during construction									(8,325)	(6,928)	(6,771)
Change in cash overdraft									0	0	(1,038)
Other									(3,931)	1,672	758
Changes in assets and liabilities
Decrease in accounts receivable									8,551	23,727	26,743
Decrease (increase) in accrued unbilled revenues									(7,184)	40,093	6,750
Decrease in fuel oil stock									4,786	34,830	28,041
Decrease (increase) in materials and supplies									750	2,821	(72)
Increase in regulatory assets									(18,273)	(24,182)	(17,000)
Increase (decrease) in accounts payable									(10,614)	(54,555)	(65,527)
Change in prepaid and accrued income taxes, tax credits and revenue taxes									2,123	(63,096)	(4,036)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability									484	1,125	(961)
Changes in other assets and liabilities									(11,350)	(32,620)	(66,687)
Net cash provided by operating activities									369,917	333,406	306,995
Cash flows from investing activities
Capital expenditures									(320,437)	(350,161)	(336,679)
Contributions in aid of construction									30,100	40,239	41,806
Advances from (to) affiliates											0
Other									2,138	1,140	1,164
Net cash used in investing activities									(288,199)	(308,782)	(293,709)
Cash flows from financing activities
Common stock dividends									(93,599)	(90,405)	(88,492)
Preferred stock dividends of Hawaiian Electric and subsidiaries									(1,995)	(1,995)	(1,995)
Proceeds from issuance of common stock									24,000	0	40,000
Proceeds from issuance of long-term debt									40,000	80,000	0
Repayment of long-term debt									0	0	(11,400)
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less										0	0
Other									(287)	(1,537)	(462)
Net cash used in financing activities									(31,881)	(13,937)	(62,349)
Net increase (decrease) in cash and equivalents									49,837	10,687	(49,063)
Cash and cash equivalents, beginning of period				$ 24,449				$ 13,762	24,449	13,762	62,825
Cash and cash equivalents, end of period	$ 74,286				$ 24,449				$ 74,286	$ 24,449	$ 13,762