Electric utility segment - Condensed consolidating statement of cash flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net income	$ 40,720	$ 34,666
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property, plant and equipment	53,091	50,051
Other amortization	8,745	2,372
Deferred income taxes	(2,889)	10,096
Allowance for equity funds used during construction	(3,294)	(2,399)
Other	2,150	(347)
Changes in assets and liabilities
Decrease (increase) in fuel oil stock	(1,704)	(7,444)
Increase in regulatory assets	(16,900)	5,909
Change in prepaid and accrued income taxes, tax credits and revenue taxes	(29,842)	(42,175)
Decrease in defined benefit pension and other postretirement benefit plans liability	(390)	1,012
Net cash provided by operating activities	34,677	46,991
Cash flows from investing activities
Capital expenditures	(133,352)	(91,242)
Contributions in aid of construction	4,330	10,650
Other	2,593	5,709
Net cash used in investing activities	(231,051)	(184,481)
Cash flows from financing activities
Common stock dividends	(33,741)	(33,713)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	120,485	2,300
Other	(4,043)	(4,857)
Net cash provided by financing activities	179,278	93,268
Net decrease in cash and cash equivalents	(17,096)	(44,222)
Cash and cash equivalents, beginning of period	261,881	278,452
Cash and cash equivalents, end of period	244,785	234,230
Hawaiian Electric Company
Cash flows from operating activities
Net income	27,745	21,735
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries	(9,350)	(8,628)
Common stock dividends received from subsidiaries	6,827	6,910
Depreciation of property, plant and equipment	34,439	32,722
Other amortization	3,237	914
Deferred income taxes	(271)	6,810
Allowance for equity funds used during construction	(2,887)	(2,056)
Other	2,868	661
Changes in assets and liabilities
Increase in accounts receivable	(13,255)	(10,724)
Decrease in accrued unbilled revenues	6,558	(4,577)
Decrease (increase) in fuel oil stock	(1,322)	(9,234)
Decrease (increase) in materials and supplies	(1,095)	(2,267)
Increase in regulatory assets	(13,256)	7,711
Increase (decrease) in accounts payable	(2,028)	21,943
Change in prepaid and accrued income taxes, tax credits and revenue taxes	(25,892)	(32,272)
Decrease in defined benefit pension and other postretirement benefit plans liability	(592)	240
Change in other assets and liabilities	2,976	(4,249)
Net cash provided by operating activities	14,702	25,639
Cash flows from investing activities
Capital expenditures	(84,226)	(64,035)
Contributions in aid of construction	3,327	8,934
Other	269	2,352
Advances (to) from affiliates	(3,000)	0
Net cash used in investing activities	(83,630)	(52,749)
Cash flows from financing activities
Common stock dividends	(25,826)	(21,942)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(270)	(270)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	104,984	(3,000)
Other	(31)	(449)
Net cash provided by financing activities	78,857	(25,661)
Net decrease in cash and cash equivalents	9,929	(52,771)
Cash and cash equivalents, beginning of period	2,059	61,388
Cash and cash equivalents, end of period	11,988	8,617
HELCO
Cash flows from operating activities
Net income	6,235	4,718
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	10,055	9,685
Other amortization	1,554	442
Deferred income taxes	(1,806)	1,700
Allowance for equity funds used during construction	(111)	(115)
Other	(103)	(138)
Changes in assets and liabilities
Increase in accounts receivable	(2,048)	1,239
Decrease in accrued unbilled revenues	758	(319)
Decrease (increase) in fuel oil stock	(803)	1,485
Decrease (increase) in materials and supplies	(550)	(1,114)
Increase in regulatory assets	(1,773)	(677)
Increase (decrease) in accounts payable	4,050	(1,721)
Change in prepaid and accrued income taxes, tax credits and revenue taxes	(1,882)	(5,352)
Decrease in defined benefit pension and other postretirement benefit plans liability	(198)	14
Change in other assets and liabilities	2,875	805
Net cash provided by operating activities	16,253	10,652
Cash flows from investing activities
Capital expenditures	(15,161)	(12,434)
Contributions in aid of construction	656	915
Other	264	78
Advances (to) from affiliates	0	(3,000)
Net cash used in investing activities	(14,241)	(14,441)
Cash flows from financing activities
Common stock dividends	(3,821)	(3,874)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(134)	(134)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	3,000	0
Other	(2)	0
Net cash provided by financing activities	(957)	(4,008)
Net decrease in cash and cash equivalents	1,055	(7,797)
Cash and cash equivalents, beginning of period	4,025	10,749
Cash and cash equivalents, end of period	5,080	2,952
Maui Electric
Cash flows from operating activities
Net income	3,319	4,114
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	5,972	5,809
Other amortization	553	593
Deferred income taxes	497	2,602
Allowance for equity funds used during construction	(296)	(228)
Other	(84)	(87)
Changes in assets and liabilities
Increase in accounts receivable	(1,396)	685
Decrease in accrued unbilled revenues	103	(1,043)
Decrease (increase) in fuel oil stock	275	305
Decrease (increase) in materials and supplies	350	15
Increase in regulatory assets	(1,871)	(1,125)
Increase (decrease) in accounts payable	3,121	(2,991)
Change in prepaid and accrued income taxes, tax credits and revenue taxes	(5,532)	(6,408)
Decrease in defined benefit pension and other postretirement benefit plans liability	(148)	10
Change in other assets and liabilities	349	197
Net cash provided by operating activities	5,212	2,448
Cash flows from investing activities
Capital expenditures	(15,070)	(8,243)
Contributions in aid of construction	347	801
Other	510	272
Advances (to) from affiliates	12,000	7,500
Net cash used in investing activities	(2,213)	330
Cash flows from financing activities
Common stock dividends	(3,006)	(2,986)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(95)	(95)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	0	0
Other	0	(208)
Net cash provided by financing activities	(3,101)	(3,289)
Net decrease in cash and cash equivalents	(102)	(511)
Cash and cash equivalents, beginning of period	6,332	2,048
Cash and cash equivalents, end of period	6,230	1,537
Other subsidiaries
Cash flows from operating activities
Net income	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
Other	0	0
Changes in assets and liabilities
Increase in accounts receivable	0	0
Decrease in accrued unbilled revenues	0	0
Decrease (increase) in fuel oil stock	0	0
Decrease (increase) in materials and supplies	0	0
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
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 (to) 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
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
Consolidating adjustments
Cash flows from operating activities
Net income	(9,325)	(8,603)
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries	9,325	8,603
Common stock dividends received from subsidiaries	(6,827)	(6,860)
Depreciation of property, plant and equipment	0	0
Other amortization	0	0
Deferred income taxes	0	(48)
Allowance for equity funds used during construction	0	0
Other	0	0
Changes in assets and liabilities
Increase in accounts receivable	1,662	1,472
Decrease in accrued unbilled revenues	0	0
Decrease (increase) in fuel oil stock	0	0
Decrease (increase) in materials and supplies	0	0
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	440	48
Decrease in defined benefit pension and other postretirement benefit plans liability	0	0
Change in other assets and liabilities	(1,662)	(1,472)
Net cash provided by operating activities	(6,387)	(6,860)
Cash flows from investing activities
Capital expenditures	0	0
Contributions in aid of construction	0	0
Other	(440)	0
Advances (to) from affiliates	(9,000)	(4,500)
Net cash used in investing activities	(9,440)	(4,500)
Cash flows from financing activities
Common stock dividends	6,827	6,860
Preferred stock dividends of Hawaiian Electric and subsidiaries	0	0
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	9,000	4,500
Other	0	0
Net cash provided by financing activities	15,827	11,360
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
Hawaiian Electric Company, Inc. and Subsidiaries
Cash flows from operating activities
Net income	27,974	21,964
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries	(25)	(25)
Common stock dividends received from subsidiaries	0	50
Depreciation of property, plant and equipment	50,466	48,216
Other amortization	5,344	1,949
Deferred income taxes	(1,580)	11,064
Allowance for equity funds used during construction	(3,294)	(2,399)
Other	2,681	436
Changes in assets and liabilities
Increase in accounts receivable	(15,037)	(7,328)
Decrease in accrued unbilled revenues	7,419	(5,939)
Decrease (increase) in fuel oil stock	(1,850)	(7,444)
Decrease (increase) in materials and supplies	(1,295)	(3,366)
Increase in regulatory assets	(16,900)	5,909
Increase (decrease) in accounts payable	5,143	17,231
Change in prepaid and accrued income taxes, tax credits and revenue taxes	(32,866)	(43,984)
Decrease in defined benefit pension and other postretirement benefit plans liability	(938)	264
Change in other assets and liabilities	4,538	(4,719)
Net cash provided by operating activities	29,780	31,879
Cash flows from investing activities
Capital expenditures	(114,457)	(84,712)
Contributions in aid of construction	4,330	10,650
Other	603	2,702
Advances (to) from affiliates	0	0
Net cash used in investing activities	(109,524)	(71,360)
Cash flows from financing activities
Common stock dividends	(25,826)	(21,942)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(499)	(499)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	116,984	1,500
Other	(33)	(657)
Net cash provided by financing activities	90,626	(21,598)
Net decrease in cash and cash equivalents	10,882	(61,079)
Cash and cash equivalents, beginning of period	12,517	74,286
Cash and cash equivalents, end of period	$ 23,399	$ 13,207