Electric utility segment - Condensed consolidating statement of cash flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities
Net income	$ 34,666	$ 32,825
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment	50,051	48,594
Other amortization	2,372	1,928
Deferred income taxes	10,096	13,008
Allowance for equity funds used during construction	(2,399)	(1,739)
Other	(347)	1,702
Changes in assets and liabilities
Decrease (increase) in fuel oil stock	(7,444)	22,812
Decrease (increase) in regulatory assets	5,909	1,585
Change in prepaid and accrued income taxes, tax credits and revenue taxes	(42,175)	(14,343)
Increase in defined benefit pension and other postretirement benefit plans liability	1,012	137
Net cash provided by operating activities	93,934	170,972
Cash flows from investing activities
Capital expenditures	(138,185)	(127,818)
Contributions in aid of construction	10,650	13,761
Other	5,709	819
Net cash used in investing activities	(231,424)	(215,251)
Cash flows from financing activities
Common stock dividends	(33,713)	(27,716)
Net increase in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	2,300	(7,578)
Other	(4,857)	(1,561)
Net cash provided by financing activities	93,268	78,544
Net increase (decrease) in cash and cash equivalents	(44,222)	34,265
Cash and cash equivalents, beginning of period	278,452	300,478
Cash and cash equivalents, end of period	234,230	334,743
Hawaiian Electric Company
Cash flows from operating activities
Net income	21,735	25,637
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings of subsidiaries	(8,628)	(7,954)
Common stock dividends received from subsidiaries	6,910	6,592
Depreciation of property, plant and equipment	32,722	31,522
Other amortization	914	1,045
Deferred income taxes	6,810	9,764
Allowance for equity funds used during construction	(2,056)	(1,406)
Other	661	1,386
Changes in assets and liabilities
Decrease (increase) in accounts receivable	(10,724)	22,606
Increase in accrued unbilled revenues	(4,577)	58
Decrease (increase) in fuel oil stock	(9,234)	14,902
Decrease (increase) in materials and supplies	(2,267)	378
Decrease (increase) in regulatory assets	7,711	79
Increase in accounts payable	59,861	24,827
Change in prepaid and accrued income taxes, tax credits and revenue taxes	(32,272)	(31,916)
Increase in defined benefit pension and other postretirement benefit plans liability	240	177
Change in other assets and liabilities	(4,249)	15,249
Net cash provided by operating activities	63,557	112,946
Cash flows from investing activities
Capital expenditures	(101,953)	(97,363)
Contributions in aid of construction	8,934	11,585
Other	2,352	22
Advances from affiliates	0	0
Net cash used in investing activities	(90,667)	(85,756)
Cash flows from financing activities
Common stock dividends	(21,942)	(23,400)
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	(3,000)	9,498
Other	(449)	8
Net cash provided by financing activities	(25,661)	(14,164)
Net increase (decrease) in cash and cash equivalents	(52,771)	13,026
Cash and cash equivalents, beginning of period	61,388	16,281
Cash and cash equivalents, end of period	8,617	29,307
HELCO
Cash flows from operating activities
Net income	4,718	4,096
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	9,685	9,449
Other amortization	442	268
Deferred income taxes	1,700	1,277
Allowance for equity funds used during construction	(115)	(127)
Other	(138)	154
Changes in assets and liabilities
Decrease (increase) in accounts receivable	1,239	2,113
Increase in accrued unbilled revenues	(319)	(326)
Decrease (increase) in fuel oil stock	1,485	2,622
Decrease (increase) in materials and supplies	(1,114)	(27)
Decrease (increase) in regulatory assets	(677)	397
Increase in accounts payable	2,735	1,652
Change in prepaid and accrued income taxes, tax credits and revenue taxes	(5,352)	(1,634)
Increase in defined benefit pension and other postretirement benefit plans liability	14	13
Change in other assets and liabilities	805	5,562
Net cash provided by operating activities	15,108	25,489
Cash flows from investing activities
Capital expenditures	(16,890)	(16,649)
Contributions in aid of construction	915	969
Other	78	23
Advances from affiliates	(3,000)	3,000
Net cash used in investing activities	(18,897)	(12,657)
Cash flows from financing activities
Common stock dividends	(3,874)	(3,302)
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	0	0
Other	0	(8)
Net cash provided by financing activities	(4,008)	(3,444)
Net increase (decrease) in cash and cash equivalents	(7,797)	9,388
Cash and cash equivalents, beginning of period	10,749	2,682
Cash and cash equivalents, end of period	2,952	12,070
Maui Electric
Cash flows from operating activities
Net income	4,114	4,062
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	5,809	5,810
Other amortization	593	461
Deferred income taxes	2,602	2,517
Allowance for equity funds used during construction	(228)	(206)
Other	(87)	162
Changes in assets and liabilities
Decrease (increase) in accounts receivable	685	3,563
Increase in accrued unbilled revenues	(1,043)	(590)
Decrease (increase) in fuel oil stock	305	5,288
Decrease (increase) in materials and supplies	15	(178)
Decrease (increase) in regulatory assets	(1,125)	1,109
Increase in accounts payable	1,578	1,287
Change in prepaid and accrued income taxes, tax credits and revenue taxes	(6,408)	(8,466)
Increase in defined benefit pension and other postretirement benefit plans liability	10	15
Change in other assets and liabilities	197	169
Net cash provided by operating activities	7,017	15,003
Cash flows from investing activities
Capital expenditures	(12,812)	(11,171)
Contributions in aid of construction	801	1,207
Other	272	0
Advances from affiliates	7,500	500
Net cash used in investing activities	(4,239)	(9,464)
Cash flows from financing activities
Common stock dividends	(2,986)	(3,265)
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	(208)	0
Net cash provided by financing activities	(3,289)	(3,360)
Net increase (decrease) in cash and cash equivalents	(511)	2,179
Cash and cash equivalents, beginning of period	2,048	5,385
Cash and cash equivalents, end of period	1,537	7,564
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
Decrease (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 in accounts payable	0	0
Change in prepaid and accrued income taxes, tax credits and revenue taxes	0	0
Increase 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
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 increase (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	(8,603)	(7,929)
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings of subsidiaries	8,603	7,929
Common stock dividends received from subsidiaries	(6,860)	(6,567)
Depreciation of property, plant and equipment	0	0
Other amortization	0	0
Deferred income taxes	(48)	0
Allowance for equity funds used during construction	0	0
Other	0	0
Changes in assets and liabilities
Decrease (increase) in accounts receivable	1,472	15
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 in accounts payable	0	0
Change in prepaid and accrued income taxes, tax credits and revenue taxes	48	(2)
Increase in defined benefit pension and other postretirement benefit plans liability	0	0
Change in other assets and liabilities	(1,472)	(13)
Net cash provided by operating activities	(6,860)	(6,567)
Cash flows from investing activities
Capital expenditures	0	0
Contributions in aid of construction	0	0
Other	0	0
Advances from affiliates	(4,500)	(3,500)
Net cash used in investing activities	(4,500)	(3,500)
Cash flows from financing activities
Common stock dividends	6,860	6,567
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	4,500	3,500
Other	0	0
Net cash provided by financing activities	11,360	10,067
Net increase (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	21,964	25,866
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	50	25
Depreciation of property, plant and equipment	48,216	46,781
Other amortization	1,949	1,774
Deferred income taxes	11,064	13,558
Allowance for equity funds used during construction	(2,399)	(1,739)
Other	436	1,702
Changes in assets and liabilities
Decrease (increase) in accounts receivable	(7,328)	28,297
Increase in accrued unbilled revenues	(5,939)	(858)
Decrease (increase) in fuel oil stock	(7,444)	22,812
Decrease (increase) in materials and supplies	(3,366)	173
Decrease (increase) in regulatory assets	5,909	1,585
Increase in accounts payable	64,174	27,766
Change in prepaid and accrued income taxes, tax credits and revenue taxes	(43,984)	(42,018)
Increase in defined benefit pension and other postretirement benefit plans liability	264	205
Change in other assets and liabilities	(4,719)	20,967
Net cash provided by operating activities	78,822	146,871
Cash flows from investing activities
Capital expenditures	(131,655)	(125,183)
Contributions in aid of construction	10,650	13,761
Other	2,702	45
Advances from affiliates	0	0
Net cash used in investing activities	(118,303)	(111,377)
Cash flows from financing activities
Common stock dividends	(21,942)	(23,400)
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	1,500	12,998
Other	(657)	0
Net cash provided by financing activities	(21,598)	(10,901)
Net increase (decrease) in cash and cash equivalents	(61,079)	24,593
Cash and cash equivalents, beginning of period	74,286	24,449
Cash and cash equivalents, end of period	$ 13,207	$ 49,042