Retirement benefits (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Defined benefit plans
Expected payments for remainder of fiscal year	$ 3,000,000		$ 3,000,000		$ 2,000,000
Retirement benefits expense			$ 29,000,000	$ 27,000,000
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			$ 3,600,000	3,200,000
Cash contributions by the employer to defined contribution plan			4,900,000	4,800,000
Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit plans
Expected payments for remainder of fiscal year	1,000,000		1,000,000		1,000,000
Retirement benefits expense			29,000,000	25,000,000
Defined contribution plan, expenses recognized			1,300,000	1,100,000
Cash contributions by the employer to defined contribution plan			1,300,000	1,100,000
Pension benefits
Defined benefit plans
Contributions made to defined benefit plans			24,000,000	32,000,000
Contributions expected to be paid in current year	48,000,000		48,000,000		39,000,000
Service cost	15,382,000	$ 17,428,000	30,764,000	34,541,000
Interest cost	21,033,000	19,459,000	42,066,000	38,693,000
Expected return on plan assets	(27,999,000)	(27,224,000)	(55,997,000)	(54,478,000)
Amortization of net prior service gain	(11,000)	(11,000)	(22,000)	(21,000)
Amortization of net actuarial (gains) losses	3,839,000	7,634,000	7,678,000	15,029,000
Net periodic pension/benefit cost (return)	12,244,000	17,286,000	24,489,000	33,764,000
Impact of PUC D&Os	12,278,000	7,179,000	24,557,000	9,836,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	24,522,000	24,465,000	49,046,000	43,600,000
Pension benefits | American Savings Bank (ASB)
Defined benefit plans
Contributions expected to be paid in current year	0		0		0
Pension benefits | Hawaiian Electric Industries, Inc.
Defined benefit plans
Contributions expected to be paid in current year	1,000,000		1,000,000		1,000,000
Pension benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit plans
Contributions made to defined benefit plans			23,000,000	32,000,000
Contributions expected to be paid in current year	47,000,000		47,000,000		$ 38,000,000
Service cost	15,001,000	17,007,000	30,002,000	33,680,000
Interest cost	19,414,000	17,937,000	38,828,000	35,647,000
Expected return on plan assets	(26,164,000)	(25,577,000)	(52,328,000)	(51,184,000)
Amortization of net prior service gain	2,000	2,000	4,000	4,000
Amortization of net actuarial (gains) losses	3,576,000	6,941,000	7,152,000	13,651,000
Net periodic pension/benefit cost (return)	11,829,000	16,310,000	23,658,000	31,798,000
Impact of PUC D&Os	12,278,000	7,179,000	24,557,000	9,836,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	24,107,000	23,489,000	48,215,000	41,634,000
Other benefits
Defined benefit plans
Service cost	542,000	692,000	1,083,000	1,361,000
Interest cost	1,997,000	2,030,000	3,994,000	3,961,000
Expected return on plan assets	(3,086,000)	(3,267,000)	(6,172,000)	(6,459,000)
Amortization of net prior service gain	(452,000)	(451,000)	(904,000)	(903,000)
Amortization of net actuarial (gains) losses	(4,000)	48,000	(7,000)	46,000
Net periodic pension/benefit cost (return)	(1,003,000)	(948,000)	(2,006,000)	(1,994,000)
Impact of PUC D&Os	811,000	1,024,000	1,622,000	2,095,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	(192,000)	76,000	(384,000)	101,000
Other benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit plans
Service cost	538,000	688,000	1,075,000	1,352,000
Interest cost	1,918,000	1,955,000	3,835,000	3,814,000
Expected return on plan assets	(3,036,000)	(3,216,000)	(6,071,000)	(6,356,000)
Amortization of net prior service gain	(451,000)	(451,000)	(902,000)	(902,000)
Amortization of net actuarial (gains) losses	0	49,000	0	49,000
Net periodic pension/benefit cost (return)	(1,031,000)	(975,000)	(2,063,000)	(2,043,000)
Impact of PUC D&Os	811,000	1,024,000	1,622,000	2,095,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	$ (220,000)	$ 49,000	$ (441,000)	$ 52,000