Retirement benefits (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Defined benefit plans
Expected payments for remainder of fiscal year	$ 2,000,000		$ 2,000,000
Retirement benefits expense			$ 25,000,000	$ 26,000,000
Number of years for which regulatory asset/liability for each utility will be amortized, beginning with respective utility's next rate case (in years)			5 years
Defined contribution plan, expenses recognized			$ 5,100,000	4,100,000
Cash contributions by the employer to defined contribution plan			5,000,000	4,600,000
Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit plans
Expected payments for remainder of fiscal year	1,000,000		1,000,000
Retirement benefits expense			22,000,000	23,000,000
Defined contribution plan, expenses recognized			1,400,000	1,200,000
Cash contributions by the employer to defined contribution plan			1,400,000	1,200,000
Pension benefits
Defined benefit plans
Contributions made to defined benefit plans			50,000,000	49,000,000
Contributions expected to be paid in current year			67,000,000		$ 65,000,000
Service cost	16,271,000	$ 15,126,000	48,635,000	45,430,000
Interest cost	20,304,000	20,396,000	60,881,000	61,154,000
Expected return on plan assets	(25,689,000)	(24,640,000)	(77,056,000)	(73,920,000)
Amortization of net prior service gain	(14,000)	(15,000)	(41,000)	(43,000)
Amortization of net actuarial loss	6,638,000	6,228,000	19,858,000	18,605,000
Net periodic pension/benefit cost	17,510,000	17,095,000	52,277,000	51,226,000
Impact of PUC D&Os	(4,534,000)	(4,653,000)	(14,557,000)	(13,464,000)
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	12,976,000	12,442,000	37,720,000	37,762,000
Pension benefits | American Savings Bank (ASB)
Defined benefit plans
Contributions expected to be paid in current year			0		0
Pension benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit plans
Contributions made to defined benefit plans			49,000,000	48,000,000
Contributions expected to be paid in current year			66,000,000		64,000,000
Service cost	15,764,000	14,699,000	47,294,000	44,097,000
Interest cost	18,659,000	18,702,000	55,974,000	56,106,000
Expected return on plan assets	(23,973,000)	(22,908,000)	(71,919,000)	(68,725,000)
Amortization of net prior service gain	2,000	3,000	6,000	10,000
Amortization of net actuarial loss	6,098,000	5,674,000	18,294,000	17,020,000
Net periodic pension/benefit cost	16,550,000	16,170,000	49,649,000	48,508,000
Impact of PUC D&Os	(4,534,000)	(4,653,000)	(14,557,000)	(13,464,000)
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	12,016,000	11,517,000	35,092,000	35,044,000
Pension benefits | Hawaiian Electric Industries, Inc.
Defined benefit plans
Contributions expected to be paid in current year			1,000,000		$ 1,000,000
Other benefits
Defined benefit plans
Service cost	843,000	831,000	2,530,000	2,499,000
Interest cost	2,363,000	2,417,000	7,089,000	7,254,000
Expected return on plan assets	(3,078,000)	(3,064,000)	(9,248,000)	(9,207,000)
Amortization of net prior service gain	(448,000)	(449,000)	(1,345,000)	(1,345,000)
Amortization of net actuarial loss	283,000	200,000	848,000	603,000
Net periodic pension/benefit cost	(37,000)	(65,000)	(126,000)	(196,000)
Impact of PUC D&Os	346,000	336,000	1,019,000	1,008,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	309,000	271,000	893,000	812,000
Other benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit plans
Service cost	839,000	821,000	2,515,000	2,463,000
Interest cost	2,279,000	2,334,000	6,837,000	7,003,000
Expected return on plan assets	(3,037,000)	(3,023,000)	(9,110,000)	(9,072,000)
Amortization of net prior service gain	(451,000)	(451,000)	(1,353,000)	(1,353,000)
Amortization of net actuarial loss	275,000	198,000	826,000	595,000
Net periodic pension/benefit cost	(95,000)	(121,000)	(285,000)	(364,000)
Impact of PUC D&Os	346,000	336,000	1,019,000	1,008,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	$ 251,000	$ 215,000	$ 734,000	$ 644,000