Electric utility segment - Condensed consolidating statement of cash flows (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities
Net income	$ 39,134	$ 44,601	$ 73,800	$ 77,426
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property, plant and equipment			100,062	97,148
Other amortization			6,101	4,840
Deferred income taxes			17,047	21,738
Allowance for equity funds used during construction	(3,027)	(1,997)	(5,426)	(3,736)
Other			246	2,982
Changes in assets and liabilities
Decrease (increase) in fuel oil stock			(5,962)	9,644
Decrease (increase) in regulatory assets			8,179	(11,752)
Change in prepaid and accrued income taxes, tax credits and revenue taxes			(37,954)	622
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			420	95
Change in other assets and liabilities			(33,922)	(18,878)
Net cash provided by operating activities			186,023	225,843
Cash flows from investing activities
Capital expenditures			(222,246)	(203,631)
Contributions in aid of construction			17,571	16,810
Other			8,216	1,106
Net cash used in investing activities			(399,442)	(384,986)
Cash flows from financing activities
Common stock dividends			(67,426)	(55,591)
Proceeds from issuance of long-term debt			265,000	75,000
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds			(265,000)	(75,000)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			49,789	12,922
Other			(3,253)	2,908
Net cash provided by financing activities			145,348	115,873
Net decrease in cash and cash equivalents			(68,071)	(43,270)
Cash and cash equivalents, beginning of period			278,452	300,478
Cash and cash equivalents, end of period	210,381	257,208	210,381	257,208
Hawaiian Electric Company
Cash flows from operating activities
Net income	25,914	36,127	47,649	61,764
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries			(16,589)	(18,862)
Common stock dividends received from subsidiaries			13,771	13,184
Depreciation of property, plant and equipment			65,445	63,044
Other amortization			1,875	1,919
Deferred income taxes			15,060	23,954
Allowance for equity funds used during construction	(2,659)	(1,559)	(4,715)	(2,965)
Other			1,089	1,383
Changes in assets and liabilities
Decrease (increase) in accounts receivable			(5,100)	14,177
Increase in accrued unbilled revenues			(8,819)	(2,941)
Decrease (increase) in fuel oil stock			(4,250)	6,015
Increase in materials and supplies			(788)	(1,748)
Decrease (increase) in regulatory assets			11,378	(3,974)
Increase in accounts payable			39,954	17,150
Change in prepaid and accrued income taxes, tax credits and revenue taxes			(29,430)	(21,371)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			355	299
Change in other assets and liabilities			(12,727)	(11,803)
Net cash provided by operating activities			114,158	139,225
Cash flows from investing activities
Capital expenditures			(153,554)	(152,283)
Contributions in aid of construction			14,078	12,824
Other			4,820	132
Advances from affiliates			0	0
Net cash used in investing activities			(134,656)	(139,327)
Cash flows from financing activities
Common stock dividends			(43,884)	(46,800)
Preferred stock dividends of Hawaiian Electric and subsidiaries			(540)	(540)
Proceeds from issuance of long-term debt			162,000
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds			(162,000)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			35,590	50,995
Other			(2,068)	8
Net cash provided by financing activities			(10,902)	3,663
Net decrease in cash and cash equivalents			(31,400)	3,561
Cash and cash equivalents, beginning of period			61,388	16,281
Cash and cash equivalents, end of period	29,988	19,842	29,988	19,842
HELCO
Cash flows from operating activities
Net income	3,765	5,353	8,483	9,449
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries			0	0
Common stock dividends received from subsidiaries			0	0
Depreciation of property, plant and equipment			19,371	18,898
Other amortization			905	911
Deferred income taxes			3,590	2,538
Allowance for equity funds used during construction	(134)	(206)	(249)	(333)
Other			699	1,611
Changes in assets and liabilities
Decrease (increase) in accounts receivable			1,182	2,007
Increase in accrued unbilled revenues			(602)	634
Decrease (increase) in fuel oil stock			94	924
Increase in materials and supplies			(1,472)	(708)
Decrease (increase) in regulatory assets			(1,575)	2,138
Increase in accounts payable			3,291	208
Change in prepaid and accrued income taxes, tax credits and revenue taxes			(6,290)	(192)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			26	27
Change in other assets and liabilities			129	11
Net cash provided by operating activities			27,582	38,123
Cash flows from investing activities
Capital expenditures			(24,744)	(27,436)
Contributions in aid of construction			1,870	1,605
Other			619	169
Advances from affiliates			(600)	(3,000)
Net cash used in investing activities			(22,855)	(28,662)
Cash flows from financing activities
Common stock dividends			(7,748)	(6,604)
Preferred stock dividends of Hawaiian Electric and subsidiaries			(267)	(267)
Proceeds from issuance of long-term debt			28,000
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds			(28,000)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			0	0
Other			(357)	(8)
Net cash provided by financing activities			(8,372)	(6,879)
Net decrease in cash and cash equivalents			(3,645)	2,582
Cash and cash equivalents, beginning of period			10,749	2,682
Cash and cash equivalents, end of period	7,104	5,264	7,104	5,264
Maui Electric
Cash flows from operating activities
Net income	4,400	5,759	8,514	9,821
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries			0	0
Common stock dividends received from subsidiaries			0	0
Depreciation of property, plant and equipment			11,556	11,599
Other amortization			1,482	963
Deferred income taxes			4,988	5,623
Allowance for equity funds used during construction	(234)	(232)	(462)	(438)
Other			(173)	(12)
Changes in assets and liabilities
Decrease (increase) in accounts receivable			(1,067)	729
Increase in accrued unbilled revenues			(2,482)	(908)
Decrease (increase) in fuel oil stock			(1,806)	2,705
Increase in materials and supplies			(1,160)	(26)
Decrease (increase) in regulatory assets			(1,624)	1,159
Increase in accounts payable			8,392	6,069
Change in prepaid and accrued income taxes, tax credits and revenue taxes			(4,725)	(6,626)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			(79)	(89)
Change in other assets and liabilities			1,807	(659)
Net cash provided by operating activities			23,161	29,910
Cash flows from investing activities
Capital expenditures			(23,782)	(17,613)
Contributions in aid of construction			1,623	2,381
Other			307	30
Advances from affiliates			9,000	(11,000)
Net cash used in investing activities			(12,852)	(26,202)
Cash flows from financing activities
Common stock dividends			(5,973)	(6,530)
Preferred stock dividends of Hawaiian Electric and subsidiaries			(191)	(191)
Proceeds from issuance of long-term debt			75,000
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds			(75,000)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			0	0
Other			(804)	0
Net cash provided by financing activities			(6,968)	(6,721)
Net decrease in cash and cash equivalents			3,341	(3,013)
Cash and cash equivalents, beginning of period			2,048	5,385
Cash and cash equivalents, end of period	5,389	2,372	5,389	2,372
Other subsidiaries
Cash flows from operating activities
Net income	0	0	0	0
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries			0	0
Common stock dividends received from subsidiaries			0	0
Depreciation of property, plant and equipment			0	0
Other amortization			0	0
Deferred income taxes			0	0
Allowance for equity funds used during construction	0	0	0	0
Other			0	0
Changes in assets and liabilities
Decrease (increase) in accounts receivable			0	0
Increase in accrued unbilled revenues			0	0
Decrease (increase) in fuel oil stock			0	0
Increase in materials and supplies			0	0
Decrease (increase) in regulatory assets			0	0
Increase in accounts payable			0	0
Change in prepaid and accrued income taxes, tax credits and revenue taxes			0	0
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			0	0
Change in other assets and liabilities			0	0
Net cash provided by operating activities			0	0
Cash flows from investing activities
Capital expenditures			0	0
Contributions in aid of construction			0	0
Other			0	0
Advances from affiliates			0	0
Net cash used in investing activities			0	0
Cash flows from financing activities
Common stock dividends			0	0
Preferred stock dividends of Hawaiian Electric and subsidiaries			0	0
Proceeds from issuance of long-term debt			0
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds			0
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			0	0
Other			0	0
Net cash provided by financing activities			0	0
Net decrease in cash and cash equivalents			0	0
Cash and cash equivalents, beginning of period			101	101
Cash and cash equivalents, end of period	101	101	101	101
Consolidating adjustments
Cash flows from operating activities
Net income	(7,936)	(10,883)	(16,539)	(18,812)
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries			16,539	18,812
Common stock dividends received from subsidiaries			(13,721)	(13,134)
Depreciation of property, plant and equipment			0	0
Other amortization			0	0
Deferred income taxes			(39)	3
Allowance for equity funds used during construction	0	0	0	0
Other			0	0
Changes in assets and liabilities
Decrease (increase) in accounts receivable			3,256	(231)
Increase in accrued unbilled revenues			0	0
Decrease (increase) in fuel oil stock			0	0
Increase in materials and supplies			0	0
Decrease (increase) in regulatory assets			0	0
Increase in accounts payable			0	0
Change in prepaid and accrued income taxes, tax credits and revenue taxes			(465)	(3)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			0	0
Change in other assets and liabilities			(3,256)	231
Net cash provided by operating activities			(14,225)	(13,134)
Cash flows from investing activities
Capital expenditures			0	0
Contributions in aid of construction			0	0
Other			504	0
Advances from affiliates			(8,400)	14,000
Net cash used in investing activities			(7,896)	14,000
Cash flows from financing activities
Common stock dividends			13,721	13,134
Preferred stock dividends of Hawaiian Electric and subsidiaries			0	0
Proceeds from issuance of long-term debt
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds			0
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			8,400	(14,000)
Other			0	0
Net cash provided by financing activities			22,121	(866)
Net decrease in cash and cash equivalents			0	0
Cash and cash equivalents, beginning of period			0	0
Cash and cash equivalents, end of period	0	0	0	0
Hawaiian Electric Company, Inc. and Subsidiaries
Cash flows from operating activities
Net income	26,143	36,356	48,107	62,222
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries			(50)	(50)
Common stock dividends received from subsidiaries			50	50
Depreciation of property, plant and equipment			96,372	93,541
Other amortization			4,262	3,793
Deferred income taxes			23,599	32,118
Allowance for equity funds used during construction	(3,027)	(1,997)	(5,426)	(3,736)
Other			1,615	2,982
Changes in assets and liabilities
Decrease (increase) in accounts receivable			(1,729)	16,682
Increase in accrued unbilled revenues			(11,903)	(3,215)
Decrease (increase) in fuel oil stock			(5,962)	9,644
Increase in materials and supplies			(3,420)	(2,482)
Decrease (increase) in regulatory assets			8,179	(677)
Increase in accounts payable			51,637	23,427
Change in prepaid and accrued income taxes, tax credits and revenue taxes			(40,910)	(28,192)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			302	237
Change in other assets and liabilities			(14,047)	(12,220)
Net cash provided by operating activities			150,676	194,124
Cash flows from investing activities
Capital expenditures			(202,080)	(197,332)
Contributions in aid of construction			17,571	16,810
Other			6,250	331
Advances from affiliates			0	0
Net cash used in investing activities			(178,259)	(180,191)
Cash flows from financing activities
Common stock dividends			(43,884)	(46,800)
Preferred stock dividends of Hawaiian Electric and subsidiaries			(998)	(998)
Proceeds from issuance of long-term debt			265,000	0
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds			(265,000)	0
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less			43,990	36,995
Other			(3,229)	0
Net cash provided by financing activities			(4,121)	(10,803)
Net decrease in cash and cash equivalents			(31,704)	3,130
Cash and cash equivalents, beginning of period			74,286	24,449
Cash and cash equivalents, end of period	$ 42,582	$ 27,579	$ 42,582	$ 27,579