Basis of presentation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	$ 669,984	$ 561,712	$ 1,850,447	$ 1,638,015
Operating income	98,064	111,473	248,752	259,013
Retirement defined benefits expense—other than service costs	(1,276)	(1,928)	(4,673)	(5,710)
Increase (decrease) in accounts, interest and dividends payable			(7,122)	18,581
Net cash provided by operating activities			257,679	320,114
Net cash used in investing activities			(541,761)	(469,330)
Capital expenditures			(404,984)	(343,375)
Hawaiian Electric Company, Inc. and Subsidiaries
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	613,373	510,272	1,685,413	1,478,915
Operating income	74,036	88,497	180,549	195,340
Retirement defined benefits expense—other than service costs	(682)	(1,421)	(2,934)	(4,279)
Other operation and maintenance	113,553	98,681	333,805	302,437
Net cash provided by operating activities			193,722	258,873
Net cash used in investing activities			(300,558)	(258,258)
Capital expenditures			(334,730)	(306,975)
Increase (decrease) in accounts payable			(8,712)	6,130
Hawaiian Electric (parent only)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		366,394		1,054,570
Operating income		62,873		131,954
Retirement defined benefits expense—other than service costs		(1,225)		(3,812)
Other operation and maintenance		64,996		200,648
Hawaii Electric Light Company, Inc. (HELCO)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		71,307		212,875
Operating income		13,027		32,151
Retirement defined benefits expense—other than service costs		15		183
Other operation and maintenance		16,608		49,850
Maui Electric
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		72,571		211,470
Operating income		12,627		31,286
Retirement defined benefits expense—other than service costs		(211)		(650)
Other operation and maintenance		17,077		51,939
American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	53,232	47,313	153,951	146,146
Operating income	27,264	26,976	79,068	76,328
Retirement defined benefits expense—other than service costs	433	212	1,223	608
Compensation and employee benefits	23,952	23,512	72,047	71,095
Other expense	4,240	5,262	12,897	14,674
Electric utility
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	613,373	510,272	1,685,413	1,478,915
Operating income	74,036	88,497	180,549	195,340
Bank
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	53,232	47,313	153,951	146,146
Operating income	27,264	26,976	79,068	76,328
Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses	3,379	4,127	11,083	12,954
Operating income	$ (3,236)	(4,000)	$ (10,865)	(12,655)
As previously filed
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		563,640		1,643,725
Operating income		109,545		253,303
Retirement defined benefits expense—other than service costs		0		0
As previously filed | Hawaiian Electric Company, Inc. and Subsidiaries
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		511,693		1,483,194
Operating income		87,076		191,061
Retirement defined benefits expense—other than service costs		0		0
Other operation and maintenance		100,102		306,716
As previously filed | Hawaiian Electric (parent only)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		367,619		1,058,382
Operating income		61,648		128,142
Retirement defined benefits expense—other than service costs		0		0
Other operation and maintenance		66,221		204,460
As previously filed | Hawaii Electric Light Company, Inc. (HELCO)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		71,292		212,692
Operating income		13,042		32,334
Retirement defined benefits expense—other than service costs		0		0
Other operation and maintenance		16,593		49,667
As previously filed | Maui Electric
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		72,782		212,120
Operating income		12,416		30,636
Retirement defined benefits expense—other than service costs		0		0
Other operation and maintenance		17,288		52,589
As previously filed | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Compensation and employee benefits		23,724		71,703
Other expense		5,050		14,066
As previously filed | Electric utility
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		511,693		1,483,194
Operating income		87,076		191,061
As previously filed | Bank
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		47,525		146,754
Operating income		26,764		75,720
As previously filed | Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		4,422		13,777
Operating income		(4,295)		(13,478)
Adjustment | Hawaiian Electric (parent only)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase (decrease) in accounts, interest and dividends payable				28,971
Net cash provided by operating activities				28,971
Net cash used in investing activities				(28,971)
Capital expenditures				(28,971)
Increase (decrease) in accounts payable				28,971
Adjustment | ASU 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(1,928)		(5,710)
Operating income		1,928		5,710
Retirement defined benefits expense—other than service costs		(1,928)		(5,710)
Adjustment | ASU 2017-07 | Hawaiian Electric Company, Inc. and Subsidiaries
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(1,421)		(4,279)
Operating income		1,421		4,279
Retirement defined benefits expense—other than service costs		(1,421)		(4,279)
Other operation and maintenance		(1,421)		(4,279)
Adjustment | ASU 2017-07 | Hawaiian Electric (parent only)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(1,225)		(3,812)
Operating income		1,225		3,812
Retirement defined benefits expense—other than service costs		(1,225)		(3,812)
Other operation and maintenance		(1,225)		(3,812)
Adjustment | ASU 2017-07 | Hawaii Electric Light Company, Inc. (HELCO)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		15		183
Operating income		(15)		(183)
Retirement defined benefits expense—other than service costs		15		183
Other operation and maintenance		15		183
Adjustment | ASU 2017-07 | Maui Electric
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(211)		(650)
Operating income		211		650
Retirement defined benefits expense—other than service costs		(211)		(650)
Other operation and maintenance		(211)		(650)
Adjustment | ASU 2017-07 | American Savings Bank (ASB)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Compensation and employee benefits		(212)		(608)
Other expense		212		608
Adjustment | ASU 2017-07 | Electric utility
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(1,421)		(4,279)
Operating income		1,421		4,279
Adjustment | ASU 2017-07 | Bank
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(212)		(608)
Operating income		212		608
Adjustment | ASU 2017-07 | Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Costs and expenses		(295)		(823)
Operating income		$ 295		$ 823