Retirement benefits Changes in Projected Benefit Obligations and Fair Value of Plan Assets and Amounts Recognized in OCI (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	$ 1,446,291	$ 1,590,304
Service cost	49,264	56,405	43,221
Interest cost	72,202	64,788	67,480
Actuarial losses (gains)	342,446	(203,302)
Benefits paid and expenses	(62,975)	(61,904)
Benefit obligation, balance at the end of the period	1,847,228	1,446,291	1,590,304
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	1,186,669	971,314
Actual return on plan assets	81,123	194,130
Employer contributions	60,103	82,083
Benefits paid and expenses	(61,835)	(60,858)
Fair value of plan assets, balance at the end of the period	1,266,060	1,186,669	971,314
Accrued benefit asset (liability), balance	(581,168)	(259,622)
Other assets	12,800	24,948
Defined benefit pension and other postretirement benefit plans liability	(593,968)	(284,570)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income [Roll Forward]
AOCI debit/(credit), balance at beginning of the period (excluding impact of PUC D&Os)	317,544	680,781
Recognized during year - net recognized transition obligation	0	0
Recognized during year - prior service credit (cost)	(88)	97
Recognized during year - net actuarial losses	(20,304)	(38,438)
Occurring during year - net actuarial losses (gains)	342,679	(324,896)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	639,831	317,544	680,781
Cumulative impact of PUC D&Os	(592,291)	(294,266)
AOCI debit/(credit), balance at end of the period	47,540	23,278
Net actuarial loss (gain)	640,015	317,639
Prior service gain	(184)	(95)
Income taxes	(18,742)	(9,180)
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	28,798	14,098
Other benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	176,099	194,135
Service cost	3,490	4,306	4,211
Interest cost	8,550	7,569	9,009
Actuarial losses (gains)	39,098	(21,743)
Benefits paid and expenses	(8,028)	(8,168)
Benefit obligation, balance at the end of the period	219,209	176,099	194,135
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	179,330	156,731
Actual return on plan assets	9,149	29,164
Employer contributions	(257)	954
Benefits paid and expenses	(7,890)	(7,519)
Fair value of plan assets, balance at the end of the period	180,332	179,330	156,731
Accrued benefit asset (liability), balance	(38,877)	3,231
Other assets	0	7,200
Defined benefit pension and other postretirement benefit plans liability	(38,877)	(3,969)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income [Roll Forward]
AOCI debit/(credit), balance at beginning of the period (excluding impact of PUC D&Os)	(21,722)	18,846
Recognized during year - net recognized transition obligation	0	0
Recognized during year - prior service credit (cost)	1,793	1,793
Recognized during year - net actuarial losses	11	(1,602)
Occurring during year - net actuarial losses (gains)	40,851	(40,759)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	20,933	(21,722)	18,846
Cumulative impact of PUC D&Os	(22,975)	19,206
AOCI debit/(credit), balance at end of the period	(2,042)	(2,516)
Net actuarial loss (gain)	35,022	(5,840)
Prior service gain	(14,089)	(15,882)
Income taxes	795	980
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	(1,247)	(1,536)
Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined benefit pension and other postretirement benefit plans liability	(595,395)	(262,162)
Hawaiian Electric Company, Inc. and Subsidiaries | Pension benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	1,320,810	1,449,445
Service cost	47,597	54,482	41,603
Interest cost	65,979	59,119	61,453
Actuarial losses (gains)	314,210	(185,185)
Benefits paid and expenses	(57,819)	(57,051)
Benefit obligation, balance at the end of the period	1,690,777	1,320,810	1,449,445
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	1,058,260	861,778
Actual return on plan assets	69,242	172,822
Employer contributions	58,948	80,325
Benefits paid and expenses	(57,445)	(56,665)
Fair value of plan assets, balance at the end of the period	1,129,005	1,058,260	861,778
Accrued benefit asset (liability), balance	(561,772)	(262,550)
Other assets	0	0
Other liabilities (short-term)	(421)	(388)
Defined benefit pension and other postretirement benefit plans liability	(561,351)	(262,162)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income [Roll Forward]
AOCI debit/(credit), balance at beginning of the period (excluding impact of PUC D&Os)	295,973	623,588
Recognized during year - net recognized transition obligation	0	0
Recognized during year - prior service credit (cost)	(62)	464
Recognized during year - net actuarial losses	(18,459)	(34,597)
Occurring during year - net actuarial losses (gains)	317,651	(293,482)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	595,103	295,973	623,588
Cumulative impact of PUC D&Os	(592,291)	(294,266)
AOCI debit/(credit), balance at end of the period	2,812	1,707
Net actuarial loss (gain)	595,017	295,825
Prior service gain	86	148
Income taxes	(1,094)	(664)
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	1,718	1,043
Hawaiian Electric Company, Inc. and Subsidiaries | Other benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	169,579	187,110
Service cost	3,392	4,163	4,014
Interest cost	8,234	7,288	8,703
Actuarial losses (gains)	38,488	(20,900)
Benefits paid and expenses	(7,933)	(8,082)
Benefit obligation, balance at the end of the period	211,760	169,579	187,110
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	176,291	154,186
Actual return on plan assets	9,036	28,700
Employer contributions	(274)	839
Benefits paid and expenses	(7,797)	(7,434)
Fair value of plan assets, balance at the end of the period	177,256	176,291	154,186
Accrued benefit asset (liability), balance	(34,504)	6,712
Other assets	0	7,200
Other liabilities (short-term)	(460)	(488)
Defined benefit pension and other postretirement benefit plans liability	(34,044)	0
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income [Roll Forward]
AOCI debit/(credit), balance at beginning of the period (excluding impact of PUC D&Os)	(21,907)	17,432
Recognized during year - net recognized transition obligation	0	0
Recognized during year - prior service credit (cost)	1,804	1,803
Recognized during year - net actuarial losses	0	(1,544)
Occurring during year - net actuarial losses (gains)	40,193	(39,598)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	20,090	(21,907)	17,432
Cumulative impact of PUC D&Os	(22,975)	19,206
AOCI debit/(credit), balance at end of the period	(2,885)	(2,701)
Net actuarial loss (gain)	34,192	(6,001)
Prior service gain	(14,102)	(15,906)
Income taxes	1,122	1,050
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	$ (1,763)	$ (1,651)