Electric utility segment - Condensed consolidating statement of cash flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities
Net cash provided by operating activities	$ 341,428	$ 257,679
Cash flows from investing activities
Capital expenditures	(332,273)	(380,623)
Other	3,495	14,258
Net cash used in investing activities	(373,434)	(541,761)
Cash flows from financing activities
Common stock dividends	(104,591)	(101,235)
Proceeds from issuance of short-term debt	64,844	85,369
Proceeds from issuance of long-term debt	208,970	100,000
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds	(204,278)	(1,867)
Net increase (decrease) in other bank borrowings with original maturities of three months or less	19,150	(17,374)
Other	(4,266)	(5,668)
Net cash provided by financing activities	39,786	194,255
Net increase (decrease) in cash and cash equivalents	7,780	(89,827)
Cash and cash equivalents, beginning of period	169,208	261,881
Cash and cash equivalents, end of period	176,988	172,054
Consolidating adjustments
Cash flows from operating activities
Net cash provided by operating activities	(18,935)	(20,812)
Cash flows from investing activities
Capital expenditures	0	0
Advances to affiliates	37,200	(10,000)
Other	0	331
Net cash used in investing activities	37,200	(9,669)
Cash flows from financing activities
Common stock dividends	18,936	20,481
Preferred stock dividends of Hawaiian Electric and subsidiaries	0	0
Proceeds from issuance of short-term debt	0
Proceeds from issuance of long-term debt	0	0
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds	0
Net increase (decrease) in other bank borrowings with original maturities of three months or less	(37,200)	10,000
Other	(1)	0
Net cash provided by financing activities	(18,265)	30,481
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 (parent only) | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by operating activities	223,733	159,876
Cash flows from investing activities
Capital expenditures	(223,803)	(225,907)
Advances to affiliates	(22,200)	(2,000)
Other	2,975	4,518
Net cash used in investing activities	(243,028)	(223,389)
Cash flows from financing activities
Common stock dividends	(75,939)	(77,479)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(810)	(810)
Proceeds from issuance of short-term debt	25,000
Proceeds from issuance of long-term debt	120,000	75,000
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds	(121,546)
Net increase (decrease) in other bank borrowings with original maturities of three months or less	77,353	68,914
Other	578	(304)
Net cash provided by financing activities	24,636	65,321
Net increase (decrease) in cash and cash equivalents	5,341	1,808
Cash and cash equivalents, beginning of period	16,732	2,059
Cash and cash equivalents, end of period	22,073	3,867
HELCO
Cash flows from financing activities
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds	(70,000)
HELCO | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by operating activities	41,694	35,203
Cash flows from investing activities
Capital expenditures	(29,119)	(40,457)
Advances to affiliates	(15,000)	0
Other	(283)	1,177
Net cash used in investing activities	(44,402)	(39,280)
Cash flows from financing activities
Common stock dividends	(7,635)	(11,467)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(400)	(400)
Proceeds from issuance of short-term debt	0
Proceeds from issuance of long-term debt	70,000	15,000
Net increase (decrease) in other bank borrowings with original maturities of three months or less	0	0
Other	123	(54)
Net cash provided by financing activities	(7,912)	3,079
Net increase (decrease) in cash and cash equivalents	(10,620)	(998)
Cash and cash equivalents, beginning of period	15,623	4,025
Cash and cash equivalents, end of period	5,003	3,027
Maui Electric
Cash flows from financing activities
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds	(10,000)
Maui Electric | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by operating activities	36,126	19,455
Cash flows from investing activities
Capital expenditures	(44,885)	(44,005)
Advances to affiliates	0	12,000
Other	(30)	3,785
Net cash used in investing activities	(44,915)	(28,220)
Cash flows from financing activities
Common stock dividends	(11,301)	(9,014)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(286)	(286)
Proceeds from issuance of short-term debt	0
Proceeds from issuance of long-term debt	10,000	10,000
Net increase (decrease) in other bank borrowings with original maturities of three months or less	22,200	2,000
Other	85	(38)
Net cash provided by financing activities	10,698	2,662
Net increase (decrease) in cash and cash equivalents	1,909	(6,103)
Cash and cash equivalents, beginning of period	3,421	6,332
Cash and cash equivalents, end of period	5,330	229
Other subsidiaries
Cash flows from financing activities
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds	0
Other subsidiaries | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by operating activities	0	0
Cash flows from investing activities
Capital expenditures	0	0
Advances to affiliates	0	0
Other	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 short-term debt	0
Proceeds from issuance of long-term debt	0	0
Net increase (decrease) in other bank borrowings 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
Hawaiian Electric Company, Inc. and Subsidiaries
Cash flows from operating activities
Net cash provided by operating activities	282,618	193,722
Cash flows from investing activities
Capital expenditures	(297,807)	(310,369)
Advances to affiliates	0	0
Other	2,662	9,811
Net cash used in investing activities	(295,145)	(300,558)
Cash flows from financing activities
Common stock dividends	(75,939)	(77,479)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(1,496)	(1,496)
Proceeds from issuance of short-term debt	25,000
Proceeds from issuance of long-term debt	200,000	100,000
Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds	(201,546)	0
Net increase (decrease) in other bank borrowings with original maturities of three months or less	62,353	80,914
Other	785	(396)
Net cash provided by financing activities	9,157	101,543
Net increase (decrease) in cash and cash equivalents	(3,370)	(5,293)
Cash and cash equivalents, beginning of period	35,877	12,517
Cash and cash equivalents, end of period	$ 32,507	$ 7,224