Shareholders' equity - Reclassification Out of AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of investment securities, net	$ (528)	$ (9,275)	$ (653)
Interest expense	94,363	88,694	90,899
Net income (loss)	(248,056)	(199,714)	(219,772)
Hawaiian Electric Company, Inc. and Subsidiaries
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	(179,637)	(171,335)	(158,835)
Amount reclassified from AOCI
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	(152,442)	61,911	(6,548)
Amount reclassified from AOCI | Hawaiian Electric Company, Inc. and Subsidiaries
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	(151,884)	61,410	(6,627)
Amount reclassified from AOCI | Net unrealized gains (losses) on securities
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of investment securities, net	(387)	(1,638)	(478)
Amount reclassified from AOCI | Net realized losses on derivatives qualifying as cash flow hedges
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	37	0	0
Amount reclassified from AOCI | Amortization of prior service credit and net losses recognized during the period in net periodic benefit cost
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	19,253	23,689	10,107
Amount reclassified from AOCI | Amortization of prior service credit and net losses recognized during the period in net periodic benefit cost | Hawaiian Electric Company, Inc. and Subsidiaries
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	19,461	21,550	9,550
Amount reclassified from AOCI | Impact of D&Os of the PUC included in regulatory assets
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	(171,345)	39,860	(16,177)
Amount reclassified from AOCI | Impact of D&Os of the PUC included in regulatory assets | Hawaiian Electric Company, Inc. and Subsidiaries
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	$ (171,345)	$ 39,860	$ (16,177)