Retirement benefits (Details) (USD $)	9 Months Ended		12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended							12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 Pension benefits	Sep. 30, 2013 Pension benefits	Sep. 30, 2014 Pension benefits	Sep. 30, 2013 Pension benefits	Sep. 30, 2014 Other benefits	Sep. 30, 2013 Other benefits	Sep. 30, 2014 Other benefits	Sep. 30, 2013 Other benefits	Sep. 30, 2013 American Savings Bank (ASB) Other benefits	Sep. 30, 2014 Hawaiian Electric Industries, Inc. Other benefits	Sep. 30, 2013 Hawaiian Electric Industries, Inc. Other benefits	Sep. 30, 2014 HECO Consolidated	Sep. 30, 2013 HECO Consolidated	Dec. 31, 2013 HECO Consolidated	Sep. 30, 2014 HECO Consolidated Pension benefits	Sep. 30, 2013 HECO Consolidated Pension benefits	Sep. 30, 2014 HECO Consolidated Pension benefits	Sep. 30, 2013 HECO Consolidated Pension benefits	Sep. 30, 2014 HECO Consolidated Other benefits	Sep. 30, 2013 HECO Consolidated Other benefits	Sep. 30, 2014 HECO Consolidated Other benefits	Sep. 30, 2013 HECO Consolidated Other benefits
Defined benefit plans
Contributions made to defined benefit plans						$ 45,000,000	$ 62,000,000													$ 44,000,000	$ 61,000,000
Contributions expected to be paid in current year										60,000,000	83,000,000	0	1,000,000	2,000,000										59,000,000	81,000,000
Expected payments in 2014	2,000,000														1,000,000
Payments for benefits			2,000,000														1,000,000
Service cost				12,306,000	14,097,000	36,958,000	42,307,000	870,000	1,077,000	2,619,000	3,229,000							11,900,000	13,620,000	35,698,000	40,861,000	848,000	1,041,000	2,544,000	3,122,000
Interest cost				18,044,000	16,187,000	54,158,000	48,600,000	2,137,000	1,891,000	6,414,000	5,677,000							16,495,000	14,780,000	49,484,000	44,339,000	2,058,000	1,822,000	6,175,000	5,466,000
Expected return on plan assets				(20,337,000)	(18,134,000)	(61,018,000)	(54,401,000)	(2,724,000)	(2,531,000)	(8,180,000)	(7,614,000)							(18,167,000)	(16,138,000)	(54,496,000)	(48,413,000)	(2,684,000)	(2,502,000)	(8,054,000)	(7,502,000)
Amortization of prior service gain				22,000	(24,000)	66,000	(73,000)	(448,000)	(448,000)	(1,345,000)	(1,345,000)							15,000	(116,000)	46,000	(348,000)	(451,000)	(451,000)	(1,353,000)	(1,353,000)
Amortization of net actuarial loss				5,064,000	9,560,000	15,240,000	28,878,000	(2,000)	398,000	(8,000)	1,203,000							4,616,000	8,649,000	13,845,000	25,948,000	0	387,000	0	1,159,000
Net periodic benefit cost				15,099,000	21,686,000	45,404,000	65,311,000	(167,000)	387,000	(500,000)	1,150,000							14,859,000	20,795,000	44,577,000	62,387,000	(229,000)	297,000	(688,000)	892,000
Impact of PUC D&Os				(3,331,000)	(9,257,000)	(9,993,000)	(28,847,000)	494,000	(332,000)	1,482,000	(1,018,000)							(3,331,000)	(9,257,000)	(9,993,000)	(28,847,000)	494,000	(332,000)	1,482,000	(1,018,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)				11,768,000	12,429,000	35,411,000	36,464,000	327,000	55,000	982,000	132,000							11,528,000	11,538,000	34,584,000	33,540,000	265,000	(35,000)	794,000	(126,000)
Retirement benefits expense	24,000,000	24,000,000													23,000,000	21,000,000
Number of years for which regulatory asset/liability for each utility will be amortized, beginning with respective utility's next rate case	5 years
Defined contribution plan, expenses recognized	3,400,000	3,100,000													700,000	400,000
Cash contributions by the employer to defined contribution plan	$ 4,200,000	$ 3,700,000													$ 700,000	$ 400,000