Electric utility segment - Condensed consolidating statement of changes in common stock equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Increase (decrease) in stockholders' equity
Beginning Balance			$ 2,066,753	$ 1,927,640
Net income for common stock	$ 60,073	$ 127,142	132,927	203,622
Other comprehensive income (loss), net of taxes	554	(1,669)	3,909	9,239
Common stock dividends			(101,149)	(100,398)
Ending Balance	2,103,022	2,068,388	2,103,022	2,068,388
Hawaiian Electric Company
Increase (decrease) in stockholders' equity
Beginning Balance			1,799,787	1,728,325
Net income for common stock	47,487	46,974	94,596	108,198
Other comprehensive income (loss), net of taxes	22	151	521	412
Common stock dividends			(65,825)	(70,199)
Common stock issuance expenses			(4)	(9)
Ending Balance	1,829,075	1,766,727	1,829,075	1,766,727
HELCO
Increase (decrease) in stockholders' equity
Beginning Balance			291,291	292,702
Net income for common stock	6,434	7,304	14,650	16,486
Other comprehensive income (loss), net of taxes	0	0	1	(1)
Common stock dividends			(11,622)	(9,906)
Common stock issuance expenses			(1)	(5)
Ending Balance	294,319	299,276	294,319	299,276
Maui Electric
Increase (decrease) in stockholders' equity
Beginning Balance			259,554	263,725
Net income for common stock	6,333	7,425	14,656	17,055
Other comprehensive income (loss), net of taxes	0	(2)	0	(4)
Common stock dividends			(8,959)	(9,795)
Common stock issuance expenses			0	0
Ending Balance	265,251	270,981	265,251	270,981
Other subsidiaries
Increase (decrease) in stockholders' equity
Beginning Balance			101	101
Net income for common stock	0	0	0	0
Other comprehensive income (loss), net of taxes	0	0	0	0
Common stock dividends			0	0
Common stock issuance expenses			0	0
Ending Balance	101	101	101	101
Consolidating adjustments
Increase (decrease) in stockholders' equity
Beginning Balance			(550,946)	(556,528)
Net income for common stock	(12,767)	(14,729)	(29,306)	(33,541)
Other comprehensive income (loss), net of taxes	0	2	(1)	5
Common stock dividends			20,581	19,701
Common stock issuance expenses			1	5
Ending Balance	(559,671)	(570,358)	(559,671)	(570,358)
Hawaiian Electric Company, Inc. and Subsidiaries
Increase (decrease) in stockholders' equity
Beginning Balance			1,799,787	1,728,325
Net income for common stock	47,487	46,974	94,596	108,198
Other comprehensive income (loss), net of taxes	22	151	521	412
Common stock dividends			(65,825)	(70,199)
Common stock issuance expenses			(4)	(9)
Ending Balance	$ 1,829,075	$ 1,766,727	$ 1,829,075	$ 1,766,727