Shareholders' equity - Reclassification Out Of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Revenues	$ (725,966)	$ (771,535)	$ (715,485)	$ (661,615)	$ (761,650)	$ (768,048)	$ (685,277)	$ (645,874)	$ (2,874,601)	$ (2,860,849)	$ (2,555,625)
Total reclassifications									(6,548)	29,340	(62,533)
Hawaiian Electric Company, Inc. and Subsidiaries
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Revenues	$ (645,333)	$ (688,330)	$ (633,784)	$ (578,495)	$ (680,563)	$ (687,409)	$ (608,126)	$ (570,427)	(2,545,942)	(2,546,525)	(2,257,566)
Total reclassifications									(6,627)	27,337	(63,793)
Bank
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Revenues									(328,570)	(314,275)	(297,640)
Electric utility
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Revenues									(2,545,942)	(2,546,525)	(2,257,566)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications									10,107	21,015	15,737
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent | Hawaiian Electric Company, Inc. and Subsidiaries
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications									9,550	19,012	14,477
Accumulated Defined Benefit Plans Adjustment, Impact Of Decision And Orders Of The Public Utility Commission Included In Regulatory Assets
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications									(16,177)	8,325	(78,724)
Accumulated Defined Benefit Plans Adjustment, Impact Of Decision And Orders Of The Public Utility Commission Included In Regulatory Assets | Hawaiian Electric Company, Inc. and Subsidiaries
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications									(16,177)	8,325	(78,724)
Amount reclassified from AOCI | Net unrealized gains (losses) on securities | Bank
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Revenues									(478)	0	0
Amount reclassified from AOCI | Unrealized gains (losses) on derivatives | Window forward contracts | Hawaiian Electric Company, Inc. and Subsidiaries
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications									0	0	454
Amount reclassified from AOCI | Unrealized gains (losses) on derivatives | Electric utility | Window forward contracts
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications									$ 0	$ 0	$ 454