Retirement benefits (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 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			$ 44,000,000	$ 43,000,000
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	4,800,000
Cash contributions by the employer to defined contribution plan			6,000,000.0	5,900,000
Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit plans
Expected payments for remainder of fiscal year	2,000,000		2,000,000		1,000,000
Retirement benefits expense			43,000,000	40,000,000
Defined contribution plan, expenses recognized			1,900,000	1,700,000
Cash contributions by the employer to defined contribution plan			1,900,000	1,700,000
Pension benefits
Defined benefit plans
Contributions made to defined benefit plans			36,000,000	38,000,000
Contributions expected to be paid in current year	49,000,000		49,000,000		39,000,000
Service cost	15,800,000	$ 17,223,000	46,564,000	51,764,000
Interest cost	21,150,000	19,340,000	63,216,000	58,033,000
Expected return on plan assets	(27,991,000)	(27,237,000)	(83,988,000)	(81,715,000)
Amortization of net prior service gain	(10,000)	(11,000)	(32,000)	(32,000)
Amortization of net actuarial (gains) losses	3,989,000	7,527,000	11,667,000	22,556,000
Net periodic pension/benefit cost (return)	12,938,000	16,842,000	37,427,000	50,606,000
Impact of PUC D&Os	11,554,000	7,785,000	36,111,000	17,621,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	24,492,000	24,627,000	73,538,000	68,227,000
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			36,000,000	37,000,000
Contributions expected to be paid in current year	48,000,000		48,000,000		$ 38,000,000
Service cost	15,344,000	16,840,000	45,346,000	50,520,000
Interest cost	19,560,000	17,824,000	58,388,000	53,471,000
Expected return on plan assets	(26,146,000)	(25,593,000)	(78,474,000)	(76,777,000)
Amortization of net prior service gain	2,000	2,000	6,000	6,000
Amortization of net actuarial (gains) losses	3,841,000	6,826,000	10,993,000	20,477,000
Net periodic pension/benefit cost (return)	12,601,000	15,899,000	36,259,000	47,697,000
Impact of PUC D&Os	11,554,000	7,785,000	36,111,000	17,621,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	24,155,000	23,684,000	72,370,000	65,318,000
Other benefits
Defined benefit plans
Service cost	573,000	680,000	1,656,000	2,041,000
Interest cost	2,006,000	1,986,000	6,000,000	5,947,000
Expected return on plan assets	(3,101,000)	(3,224,000)	(9,273,000)	(9,683,000)
Amortization of net prior service gain	(451,000)	(451,000)	(1,355,000)	(1,354,000)
Amortization of net actuarial (gains) losses	(3,000)	25,000	(10,000)	71,000
Net periodic pension/benefit cost (return)	(976,000)	(984,000)	(2,982,000)	(2,978,000)
Impact of PUC D&Os	821,000	953,000	2,443,000	3,048,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	(155,000)	(31,000)	(539,000)	70,000
Other benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit plans
Service cost	568,000	676,000	1,643,000	2,028,000
Interest cost	1,920,000	1,907,000	5,755,000	5,721,000
Expected return on plan assets	(3,064,000)	(3,178,000)	(9,135,000)	(9,534,000)
Amortization of net prior service gain	(451,000)	(451,000)	(1,353,000)	(1,353,000)
Amortization of net actuarial (gains) losses	0	25,000	0	74,000
Net periodic pension/benefit cost (return)	(1,027,000)	(1,021,000)	(3,090,000)	(3,064,000)
Impact of PUC D&Os	821,000	953,000	2,443,000	3,048,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	$ (206,000)	$ (68,000)	$ (647,000)	$ (16,000)