Basis of presentation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	$ 573,985	$ 521,824
Operating income	71,889	69,738
Retirement defined benefits expense—other than service costs	(1,833)	(1,876)
Increase in accounts, interest and dividends payable	22,808	24,903
Net cash provided by operating activities	34,677	46,991
Capital expenditures	(133,352)	(91,242)
Net cash used in investing activities	(231,051)	(184,481)
Hawaiian Electric Company, Inc. and Subsidiaries
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	519,058	468,250
Operating income	51,369	50,361
Retirement defined benefits expense—other than service costs	(1,264)	(1,423)
Other operation and maintenance	107,610	98,817
Net cash provided by operating activities	29,780	31,879
Capital expenditures	(114,457)	(84,712)
Net cash used in investing activities	(109,524)	(71,360)
Increase (decrease) in accounts payable	5,143	17,231
Hawaiian Electric Company
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	367,414	331,903
Operating income	33,766	30,940
Retirement defined benefits expense—other than service costs	(1,062)	(1,285)
Other operation and maintenance	72,940	65,993
Net cash provided by operating activities	14,702	25,639
Capital expenditures	(84,226)	(64,035)
Net cash used in investing activities	(83,630)	(52,749)
Increase (decrease) in accounts payable	(2,028)	21,943
Hawaii Electric Light Company, Inc. (HELCO)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	76,686	68,580
Operating income	11,247	10,402
Retirement defined benefits expense—other than service costs	(103)	83
Other operation and maintenance	16,098	15,599
Net cash provided by operating activities	16,253	10,652
Capital expenditures	(15,161)	(12,434)
Net cash used in investing activities	(14,241)	(14,441)
Increase (decrease) in accounts payable	4,050	(1,721)
Maui Electric
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	74,958	67,767
Operating income	6,398	9,026
Retirement defined benefits expense—other than service costs	(99)	(221)
Other operation and maintenance	18,572	17,225
Net cash provided by operating activities	5,212	2,448
Capital expenditures	(15,070)	(8,243)
Net cash used in investing activities	(2,213)	330
Increase (decrease) in accounts payable	3,121	(2,991)
American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	50,532	48,501
Operating income	24,887	24,355
Retirement defined benefits expense—other than service costs	387	195
Compensation and employee benefits	24,440	23,042
Other expense	4,101	4,506
Electric utility
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	519,058	468,250
Operating income	51,369	50,361
Bank
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	50,532	48,501
Operating income	24,887	24,355
Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	4,395	5,073
Operating income	$ (4,367)	(4,978)
As previously filed
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		523,700
Operating income		67,862
Retirement defined benefits expense—other than service costs		0
As previously filed | Hawaiian Electric Company, Inc. and Subsidiaries
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		469,673
Operating income		48,938
Retirement defined benefits expense—other than service costs		0
Other operation and maintenance		100,240
As previously filed | Hawaiian Electric Company
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		333,188
Operating income		29,655
Retirement defined benefits expense—other than service costs		0
Other operation and maintenance		67,278
As previously filed | Hawaii Electric Light Company, Inc. (HELCO)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		68,497
Operating income		10,485
Retirement defined benefits expense—other than service costs		0
Other operation and maintenance		15,516
As previously filed | Maui Electric
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		67,988
Operating income		8,805
Retirement defined benefits expense—other than service costs		0
Other operation and maintenance		17,446
As previously filed | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Compensation and employee benefits		23,237
Other expense		4,311
As previously filed | Electric utility
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		469,673
Operating income		48,938
As previously filed | Bank
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		48,696
Operating income		24,160
As previously filed | Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		5,331
Operating income		(5,236)
Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in accounts, interest and dividends payable		(46,943)
Net cash provided by operating activities		(46,943)
Capital expenditures		46,943
Net cash used in investing activities		46,943
Adjustment | Hawaiian Electric Company
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities		(46,943)
Capital expenditures		46,943
Net cash used in investing activities		46,943
Increase (decrease) in accounts payable		(46,943)
Adjustment | ASU 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(1,876)
Operating income		1,876
Retirement defined benefits expense—other than service costs		(1,876)
Adjustment | ASU 2017-07 | Hawaiian Electric Company, Inc. and Subsidiaries
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(1,423)
Operating income		1,423
Retirement defined benefits expense—other than service costs		(1,423)
Other operation and maintenance		(1,423)
Adjustment | ASU 2017-07 | Hawaiian Electric Company
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(1,285)
Operating income		1,285
Retirement defined benefits expense—other than service costs		(1,285)
Other operation and maintenance		(1,285)
Adjustment | ASU 2017-07 | Hawaii Electric Light Company, Inc. (HELCO)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		83
Operating income		(83)
Retirement defined benefits expense—other than service costs		83
Other operation and maintenance		83
Adjustment | ASU 2017-07 | Maui Electric
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(221)
Operating income		221
Retirement defined benefits expense—other than service costs		(221)
Other operation and maintenance		(221)
Adjustment | ASU 2017-07 | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Compensation and employee benefits		(195)
Other expense		195
Adjustment | ASU 2017-07 | Electric utility
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(1,423)
Operating income		1,423
Adjustment | ASU 2017-07 | Bank
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(195)
Operating income		195
Adjustment | ASU 2017-07 | Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(258)
Operating income		$ 258