Retirement benefits (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Defined benefit plans
Expected payments	$ 2,000,000		$ 2,000,000
Payments for benefits					$ 2,000,000
Retirement benefits expense			$ 18,000,000	$ 17,000,000
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			$ 2,700,000	2,200,000
Cash contributions by the employer to defined contribution plan			3,400,000	3,500,000
Pension benefits
Defined benefit plans
Contributions made to defined benefit plans			44,000,000	30,000,000
Service cost	16,640,000	$ 12,525,000	33,106,000	24,652,000
Interest cost	19,363,000	18,113,000	38,502,000	36,114,000
Expected return on plan assets	(22,149,000)	(20,334,000)	(44,300,000)	(40,681,000)
Amortization of prior service gain	1,000	22,000	2,000	44,000
Amortization of net actuarial loss	9,455,000	5,138,000	18,417,000	10,176,000
Net periodic benefit cost	23,310,000	15,464,000	45,727,000	30,305,000
Impact of PUC D&Os	(10,464,000)	(3,651,000)	(19,977,000)	(6,662,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	12,846,000	11,813,000	25,750,000	23,643,000
Other benefits
Defined benefit plans
Contributions expected to be paid in current year			88,000,000		60,000,000
Service cost	1,094,000	866,000	1,963,000	1,749,000
Interest cost	2,268,000	2,117,000	4,503,000	4,277,000
Expected return on plan assets	(2,934,000)	(2,748,000)	(5,841,000)	(5,456,000)
Amortization of prior service gain	(449,000)	(449,000)	(897,000)	(897,000)
Amortization of net actuarial loss	466,000	(3,000)	896,000	(6,000)
Net periodic benefit cost	445,000	(217,000)	624,000	(333,000)
Impact of PUC D&Os	(218,000)	543,000	(120,000)	988,000
Net periodic benefit cost (adjusted for impact of PUC D&Os)	227,000	326,000	504,000	655,000
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	1,000,000		1,000,000
Payments for benefits					1,000,000
Retirement benefits expense			15,000,000	16,000,000
Defined contribution plan, expenses recognized			700,000	400,000
Cash contributions by the employer to defined contribution plan			700,000	400,000
HECO Consolidated | Pension benefits
Defined benefit plans
Contributions made to defined benefit plans			43,000,000	29,000,000
Service cost	16,148,000	12,101,000	32,131,000	23,798,000
Interest cost	17,749,000	16,553,000	35,265,000	32,989,000
Expected return on plan assets	(20,639,000)	(18,158,000)	(41,271,000)	(36,329,000)
Amortization of prior service gain	10,000	16,000	20,000	31,000
Amortization of net actuarial loss	8,592,000	4,669,000	16,686,000	9,229,000
Net periodic benefit cost	21,860,000	15,181,000	42,831,000	29,718,000
Impact of PUC D&Os	(10,464,000)	(3,651,000)	(19,977,000)	(6,662,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	11,396,000	11,530,000	22,854,000	23,056,000
HECO Consolidated | Other benefits
Defined benefit plans
Contributions expected to be paid in current year			86,000,000		$ 59,000,000
Service cost	1,080,000	840,000	1,935,000	1,696,000
Interest cost	2,191,000	2,038,000	4,350,000	4,117,000
Expected return on plan assets	(2,889,000)	(2,707,000)	(5,748,000)	(5,370,000)
Amortization of prior service gain	(451,000)	(451,000)	(902,000)	(902,000)
Amortization of net actuarial loss	455,000	0	877,000	0
Net periodic benefit cost	386,000	(280,000)	512,000	(459,000)
Impact of PUC D&Os	(218,000)	543,000	(120,000)	988,000
Net periodic benefit cost (adjusted for impact of PUC D&Os)	$ 168,000	$ 263,000	$ 392,000	$ 529,000