Revenues (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
General payment period									30 days
Disaggregation of Revenue [Line Items]
General payment period									30 days
Revenues from contracts with customers									$ 2,269,451	$ 2,622,025
Revenues from other sources									310,324	251,923
Revenues	$ 652,217	$ 641,427	$ 608,945	$ 677,186	$ 725,966	$ 770,882	$ 715,485	$ 661,615	2,579,775	2,873,948	$ 2,860,849
Services/goods transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									38,887	46,659
Services/goods transferred over time
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									2,230,564	2,575,366
Electric energy sales - residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									766,609	807,652
Electric energy sales - commercial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									703,516	846,110
Electric energy sales - large light and power
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									751,464	905,308
Electric energy sales - other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									8,054	16,296
Bank fees
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									38,887	46,659
Other sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									921	0
Regulatory revenue
Disaggregation of Revenue [Line Items]
Revenues from other sources									11,869	(54,101)
Bank interest and dividend income
Disaggregation of Revenue [Line Items]
Revenues from other sources									244,663	266,554
Other bank noninterest income
Disaggregation of Revenue [Line Items]
Revenues from other sources									29,961	14,704
Other
Disaggregation of Revenue [Line Items]
Revenues from other sources									23,831	24,766
Hawaiian Electric Company, Inc. and Subsidiaries
Disaggregation of Revenue [Line Items]
Revenue taxes, other than income tax expense									202,000	226,000	226,000
Revenue taxes accrued	$ 111,000				$ 132,000				111,000	132,000
Electric utility
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									2,229,643	2,575,366
Revenues from other sources									35,677	(29,424)
Revenues									2,265,320	2,545,942	2,546,525
Electric utility | Services/goods transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Electric utility | Services/goods transferred over time
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									2,229,643	2,575,366
Electric utility | Electric energy sales - residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									766,609	807,652
Electric utility | Electric energy sales - commercial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									703,516	846,110
Electric utility | Electric energy sales - large light and power
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									751,464	905,308
Electric utility | Electric energy sales - other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									8,054	16,296
Electric utility | Bank fees
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Electric utility | Other sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Electric utility | Regulatory revenue
Disaggregation of Revenue [Line Items]
Revenues from other sources									11,869	(54,101)
Electric utility | Bank interest and dividend income
Disaggregation of Revenue [Line Items]
Revenues from other sources									0	0
Electric utility | Other bank noninterest income
Disaggregation of Revenue [Line Items]
Revenues from other sources									0	0
Electric utility | Other
Disaggregation of Revenue [Line Items]
Revenues from other sources									23,808	24,677
Bank
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									38,887	46,659
Revenues from other sources									274,624	281,258
Revenues									313,511	327,917	314,275
Bank | Services/goods transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									38,887	46,659
Bank | Services/goods transferred over time
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Bank | Electric energy sales - residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Bank | Electric energy sales - commercial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Bank | Electric energy sales - large light and power
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Bank | Electric energy sales - other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Bank | Bank fees
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									38,887	46,659
Bank | Other sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Bank | Regulatory revenue
Disaggregation of Revenue [Line Items]
Revenues from other sources									0	0
Bank | Bank interest and dividend income
Disaggregation of Revenue [Line Items]
Revenues from other sources									244,663	266,554
Bank | Other bank noninterest income
Disaggregation of Revenue [Line Items]
Revenues from other sources									29,961	14,704
Bank | Other
Disaggregation of Revenue [Line Items]
Revenues from other sources									0	0
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									921	0
Revenues from other sources									23	89
Revenues									944	89	$ 49
Other | Services/goods transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Other | Services/goods transferred over time
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									921	0
Other | Electric energy sales - residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Other | Electric energy sales - commercial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Other | Electric energy sales - large light and power
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Other | Electric energy sales - other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Other | Bank fees
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									0	0
Other | Other sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									921	0
Other | Regulatory revenue
Disaggregation of Revenue [Line Items]
Revenues from other sources									0	0
Other | Bank interest and dividend income
Disaggregation of Revenue [Line Items]
Revenues from other sources									0	0
Other | Other bank noninterest income
Disaggregation of Revenue [Line Items]
Revenues from other sources									0	0
Other | Other
Disaggregation of Revenue [Line Items]
Revenues from other sources									$ 23	$ 89