Electric utility segment - Condensed consolidating statement of cash flows (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities
Net income	$ 60,544	$ 127,613	$ 134,344	$ 205,039
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property, plant and equipment			150,123	145,684
Other amortization			15,362	7,368
Deferred income taxes			21,397	30,667
Allowance for equity funds used during construction	(3,482)	(2,274)	(8,908)	(6,010)
Other			(1,350)	3,234
Changes in assets and liabilities
Decrease (increase) in fuel oil stock			6,177	6,736
Decrease (increase) in regulatory assets			3,922	(2,251)
Change in prepaid and accrued income taxes, tax credits and revenue taxes			2,828	52,558
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			670	150
Change in other assets and liabilities			(22,311)	(39,850)
Net cash provided by operating activities			291,143	409,300
Cash flows from investing activities
Capital expenditures			(314,404)	(259,207)
Contributions in aid of construction			40,603	23,568
Other			1,345	112
Net cash used in investing activities			(440,359)	(535,744)
Cash flows from financing activities
Common stock dividends			(101,149)	(83,620)
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			24,498	(103,063)
Other			(9,531)	(2,361)
Net cash provided by financing activities			72,937	110,321
Net decrease in cash and cash equivalents			(76,279)	(16,123)
Cash and cash equivalents, beginning of period			278,452	300,478
Cash and cash equivalents, end of period	202,173	284,355	202,173	284,355
Hawaiian Electric Company
Cash flows from operating activities
Net income	47,757	47,244	95,406	109,008
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries			(29,381)	(33,616)
Common stock dividends received from subsidiaries			20,656	19,776
Depreciation of property, plant and equipment			98,167	94,564
Other amortization			2,168	2,462
Deferred income taxes			12,166	41,005
Allowance for equity funds used during construction	(3,108)	(1,806)	(7,823)	(4,771)
Other			216	2,925
Changes in assets and liabilities
Increase in accounts receivable			(6,114)	328
Increase in accrued unbilled revenues			(14,823)	(9,673)
Decrease (increase) in fuel oil stock			6,779	4,157
Decrease (increase) in materials and supplies			1,063	(1,755)
Decrease (increase) in regulatory assets			9,471	(2,474)
Increase (decrease) in accounts payable			(22,224)	(2,628)
Change in prepaid and accrued income taxes, tax credits and revenue taxes			10,920	(7,324)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			532	449
Change in other assets and liabilities			(2,709)	(10,548)
Net cash provided by operating activities			174,470	201,885
Cash flows from investing activities
Capital expenditures			(207,493)	(188,415)
Contributions in aid of construction			34,787	18,181
Other			6,089	901
Advances from affiliates			0	0
Net cash used in investing activities			(166,617)	(169,333)
Cash flows from financing activities
Common stock dividends			(65,825)	(70,199)
Preferred stock dividends of Hawaiian Electric and subsidiaries			(810)	(810)
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			3,100	32,000
Other			(2,252)	(3)
Net cash provided by financing activities			(65,787)	(39,012)
Net decrease in cash and cash equivalents			(57,934)	(6,460)
Cash and cash equivalents, beginning of period			61,388	16,281
Cash and cash equivalents, end of period	3,454	9,821	3,454	9,821
HELCO
Cash flows from operating activities
Net income	6,567	7,437	15,050	16,886
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			29,056	28,347
Other amortization			1,718	1,366
Deferred income taxes			5,237	4,529
Allowance for equity funds used during construction	(167)	(238)	(416)	(571)
Other			566	162
Changes in assets and liabilities
Increase in accounts receivable			(1,127)	(2,716)
Increase in accrued unbilled revenues			(1,581)	(373)
Decrease (increase) in fuel oil stock			195	1,425
Decrease (increase) in materials and supplies			(1,580)	(1,559)
Decrease (increase) in regulatory assets			(2,935)	(150)
Increase (decrease) in accounts payable			(2,955)	143
Change in prepaid and accrued income taxes, tax credits and revenue taxes			(758)	2,230
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			39	40
Change in other assets and liabilities			1,059	2,856
Net cash provided by operating activities			41,568	52,615
Cash flows from investing activities
Capital expenditures			(36,405)	(37,835)
Contributions in aid of construction			3,460	2,691
Other			871	169
Advances from affiliates			(3,100)	(3,000)
Net cash used in investing activities			(35,174)	(37,975)
Cash flows from financing activities
Common stock dividends			(11,622)	(9,906)
Preferred stock dividends of Hawaiian Electric and subsidiaries			(400)	(400)
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			(407)	(8)
Net cash provided by financing activities			(12,429)	(10,314)
Net decrease in cash and cash equivalents			(6,035)	4,326
Cash and cash equivalents, beginning of period			10,749	2,682
Cash and cash equivalents, end of period	4,714	7,008	4,714	7,008
Maui Electric
Cash flows from operating activities
Net income	6,428	7,520	14,942	17,341
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			17,355	17,389
Other amortization			2,232	1,552
Deferred income taxes			7,493	10,085
Allowance for equity funds used during construction	(207)	(230)	(669)	(668)
Other			(256)	147
Changes in assets and liabilities
Increase in accounts receivable			(1,912)	(1,313)
Increase in accrued unbilled revenues			(1,610)	(612)
Decrease (increase) in fuel oil stock			(797)	1,154
Decrease (increase) in materials and supplies			(1,763)	387
Decrease (increase) in regulatory assets			(2,614)	373
Increase (decrease) in accounts payable			2,338	1,809
Change in prepaid and accrued income taxes, tax credits and revenue taxes			210	(4,472)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			(118)	(129)
Change in other assets and liabilities			54	(2,571)
Net cash provided by operating activities			34,885	40,472
Cash flows from investing activities
Capital expenditures			(34,106)	(24,454)
Contributions in aid of construction			2,356	2,696
Other			714	30
Advances from affiliates			6,000	(8,000)
Net cash used in investing activities			(25,036)	(29,728)
Cash flows from financing activities
Common stock dividends			(8,959)	(9,795)
Preferred stock dividends of Hawaiian Electric and subsidiaries			(286)	(286)
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			(934)	(1)
Net cash provided by financing activities			(10,179)	(10,082)
Net decrease in cash and cash equivalents			(330)	662
Cash and cash equivalents, beginning of period			2,048	5,385
Cash and cash equivalents, end of period	1,718	6,047	1,718	6,047
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
Increase in accounts receivable			0	0
Increase in accrued unbilled revenues			0	0
Decrease (increase) in fuel oil stock			0	0
Decrease (increase) in materials and supplies			0	0
Decrease (increase) in regulatory assets			0	0
Increase (decrease) 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	(12,767)	(14,729)	(29,306)	(33,541)
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries			29,306	33,541
Common stock dividends received from subsidiaries			(20,581)	(19,701)
Depreciation of property, plant and equipment			0	0
Other amortization			0	0
Deferred income taxes			4,641	29
Allowance for equity funds used during construction	0	0	0	0
Other			0	0
Changes in assets and liabilities
Increase in accounts receivable			1,066	3,046
Increase in accrued unbilled revenues			0	0
Decrease (increase) in fuel oil stock			0	0
Decrease (increase) in materials and supplies			0	0
Decrease (increase) in regulatory assets			0	0
Increase (decrease) in accounts payable			0	0
Change in prepaid and accrued income taxes, tax credits and revenue taxes			(5,081)	(29)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			0	0
Change in other assets and liabilities			(1,066)	(3,046)
Net cash provided by operating activities			(21,021)	(19,701)
Cash flows from investing activities
Capital expenditures			0	0
Contributions in aid of construction			0	0
Other			440	0
Advances from affiliates			(2,900)	11,000
Net cash used in investing activities			(2,460)	11,000
Cash flows from financing activities
Common stock dividends			20,581	19,701
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			2,900	(11,000)
Other			0	0
Net cash provided by financing activities			23,481	8,701
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	47,985	47,472	96,092	109,694
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries			(75)	(75)
Common stock dividends received from subsidiaries			75	75
Depreciation of property, plant and equipment			144,578	140,300
Other amortization			6,118	5,380
Deferred income taxes			29,537	55,648
Allowance for equity funds used during construction	(3,482)	(2,274)	(8,908)	(6,010)
Other			526	3,234
Changes in assets and liabilities
Increase in accounts receivable			(8,087)	(655)
Increase in accrued unbilled revenues			(18,014)	(10,658)
Decrease (increase) in fuel oil stock			6,177	6,736
Decrease (increase) in materials and supplies			(2,280)	(2,927)
Decrease (increase) in regulatory assets			3,922	(2,251)
Increase (decrease) in accounts payable			(22,841)	(676)
Change in prepaid and accrued income taxes, tax credits and revenue taxes			5,291	(9,595)
Increase (decrease) in defined benefit pension and other postretirement benefit plans liability			453	360
Change in other assets and liabilities			(2,662)	(13,309)
Net cash provided by operating activities			229,902	275,271
Cash flows from investing activities
Capital expenditures			(278,004)	(250,704)
Contributions in aid of construction			40,603	23,568
Other			8,114	1,100
Advances from affiliates			0	0
Net cash used in investing activities			(229,287)	(226,036)
Cash flows from financing activities
Common stock dividends			(65,825)	(70,199)
Preferred stock dividends of Hawaiian Electric and subsidiaries			(1,496)	(1,496)
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			6,000	21,000
Other			(3,593)	(12)
Net cash provided by financing activities			(64,914)	(50,707)
Net decrease in cash and cash equivalents			(64,299)	(1,472)
Cash and cash equivalents, beginning of period			74,286	24,449
Cash and cash equivalents, end of period	$ 9,987	$ 22,977	$ 9,987	$ 22,977