Electric utility segment Consolidating Statements of Changes in Common Stock Equity (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Beginning Balance				$ 1,727,070				$ 1,593,865	$ 1,727,070	$ 1,593,865	$ 1,528,706
Net income for common stock	$ 33,157	$ 47,815	$ 41,421	45,927	$ 39,013	$ 48,236	$ 40,588	33,679	168,320	161,516	138,658
Other comprehensive income (loss), net of tax benefits									(10,628)	9,673	(7,286)
Issuance of common stock, net of expenses									2,461	41,692	41,295
Common stock dividends									(126,505)	(122,626)	(120,150)
Ending Balance	1,791,428				1,727,070				1,791,428	1,727,070	1,593,865
HECO
Beginning Balance				1,593,564				1,472,136	1,593,564	1,472,136	1,402,841
Net income for common stock									137,641	122,929	99,276
Other comprehensive income (loss), net of tax benefits									(563)	1,578	(938)
Issuance of common stock, net of expenses									39,994	78,499	44,001
Common stock dividends									(88,492)	(81,578)	(73,044)
Ending Balance	1,682,144				1,593,564				1,682,144	1,593,564	1,472,136
HELCO
Beginning Balance				274,802				268,908	274,802	268,908	280,468
Net income for common stock									18,689	20,136	16,212
Other comprehensive income (loss), net of tax benefits									(18)	145	(34)
Issuance of common stock, net of expenses											0
Common stock dividends									(11,627)	(14,387)	(27,738)
Ending Balance	281,846				274,802				281,846	274,802	268,908
MECO
Beginning Balance				248,771				228,927	248,771	228,927	235,568
Net income for common stock									22,275	21,277	12,627
Other comprehensive income (loss), net of tax benefits									(5)	123	(71)
Issuance of common stock, net of expenses										12,461	0
Common stock dividends									(14,349)	(14,017)	(19,197)
Ending Balance	256,692				248,771				256,692	248,771	228,927
Other subsidiaries
Beginning Balance				101				104	101	104	107
Net income for common stock									0	(3)	(3)
Other comprehensive income (loss), net of tax benefits											0
Issuance of common stock, net of expenses											0
Ending Balance	101				101				101	101	104
Consolidating adjustments
Beginning Balance				(523,674)				(497,939)	(523,674)	(497,939)	(516,143)
Net income for common stock									(40,964)	(41,410)	(28,836)
Other comprehensive income (loss), net of tax benefits									23	(268)	105
Issuance of common stock, net of expenses										(12,461)	0
Common stock dividends									25,976	28,404	46,935
Ending Balance	(538,639)				(523,674)				(538,639)	(523,674)	(497,939)
HECO Consolidated
Beginning Balance				1,593,564				1,472,136	1,593,564	1,472,136	1,402,841
Net income for common stock	29,112	$ 38,879	$ 34,230	$ 35,420	31,990	$ 37,817	$ 28,693	$ 24,429	137,641	122,929	99,276
Other comprehensive income (loss), net of tax benefits									(563)	1,578	(938)
Issuance of common stock, net of expenses									39,994	78,499	44,001
Common stock dividends									(88,492)	(81,578)	(73,044)
Ending Balance	$ 1,682,144				$ 1,593,564				$ 1,682,144	$ 1,593,564	$ 1,472,136