Retirement benefits (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Defined benefit plans
Expected payments in 2014	$ 2,000,000
Payments for benefits			2,000,000
Retirement benefits expense	9,000,000	8,000,000
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	1,400,000	1,100,000
Cash contributions by the employer to defined contribution plan	2,500,000	2,800,000
Pension benefits
Defined benefit plans
Contributions made to defined benefit plans	21,000,000	15,000,000
Service cost	16,466,000	12,127,000
Interest cost	19,139,000	18,001,000
Expected return on plan assets	(22,151,000)	(20,347,000)
Amortization of prior service gain	1,000	22,000
Amortization of net actuarial loss	8,962,000	5,038,000
Net periodic benefit cost	22,417,000	14,841,000
Impact of PUC D&Os	(9,513,000)	(3,011,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	12,904,000	11,830,000
Other benefits
Defined benefit plans
Contributions expected to be paid in current year	86,000,000		60,000,000
Service cost	869,000	883,000
Interest cost	2,235,000	2,160,000
Expected return on plan assets	(2,907,000)	(2,708,000)
Amortization of prior service gain	(448,000)	(448,000)
Amortization of net actuarial loss	430,000	(3,000)
Net periodic benefit cost	179,000	(116,000)
Impact of PUC D&Os	98,000	445,000
Net periodic benefit cost (adjusted for impact of PUC D&Os)	277,000	329,000
American Savings Bank (ASB) | Other benefits
Defined benefit plans
Contributions expected to be paid in current year	0		0
Hawaiian Electric Industries, Inc. | Other benefits
Defined benefit plans
Contributions expected to be paid in current year	2,000,000		1,000,000
HECO Consolidated
Defined benefit plans
Expected payments in 2014	1,000,000
Payments for benefits			1,000,000
Retirement benefits expense	8,000,000	8,000,000
Defined contribution plan, expenses recognized	400,000	200,000
Cash contributions by the employer to defined contribution plan	400,000	200,000
HECO Consolidated | Pension benefits
Defined benefit plans
Contributions made to defined benefit plans	21,000,000	14,000,000
Service cost	15,983,000	11,697,000
Interest cost	17,516,000	16,436,000
Expected return on plan assets	(20,632,000)	(18,171,000)
Amortization of prior service gain	10,000	15,000
Amortization of net actuarial loss	8,094,000	4,560,000
Net periodic benefit cost	20,971,000	14,537,000
Impact of PUC D&Os	(9,513,000)	(3,011,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	11,458,000	11,526,000
HECO Consolidated | Other benefits
Defined benefit plans
Contributions expected to be paid in current year	84,000,000		59,000,000
Service cost	855,000	856,000
Interest cost	2,159,000	2,079,000
Expected return on plan assets	(2,859,000)	(2,663,000)
Amortization of prior service gain	(451,000)	(451,000)
Amortization of net actuarial loss	422,000	0
Net periodic benefit cost	126,000	(179,000)
Impact of PUC D&Os	98,000	445,000
Net periodic benefit cost (adjusted for impact of PUC D&Os)	$ 224,000	$ 266,000