Electric utility segment - Consolidating Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Utility property, plant and equipment
Total property, plant and equipment, net	$ 5,392,068	$ 5,265,735
Current assets
Cash and cash equivalents	305,551	341,421	$ 196,813
Restricted cash	5,900	17,600
Other long-term assets
Operating lease right-of-use-assets	122,416	153,069
Total assets	15,822,637	15,004,007	13,745,251
Capitalization
Common stock equity	2,390,884	2,337,502	2,280,260	$ 2,162,280
Cumulative preferred stock–not subject to mandatory redemption	0	0
Current liabilities
Interest and dividends payable	19,889	23,547
Deferred credits and other liabilities
Deferred income taxes	384,760	395,089
Total capitalization and liabilities	15,822,637	15,004,007
Hawaiian Electric (parent only)
Utility property, plant and equipment
Total property, plant and equipment, net	2,052	2,456
Other long-term assets
Total assets	3,062,073	2,930,236
Capitalization
Common stock equity	2,390,884	2,337,502
Cumulative preferred stock–not subject to mandatory redemption	0	0
Current liabilities
Short-term borrowings from non-affiliate	0	14,909
Deferred credits and other liabilities
Total capitalization and liabilities	3,062,073	2,930,236
Hawaiian Electric Company, Inc. and Subsidiaries
Utility property, plant and equipment
Land	51,937	51,611
Plant and equipment	7,735,983	7,509,343
Less accumulated depreciation	(2,940,517)	(2,819,079)
Construction in progress	204,569	188,342
Utility property, plant and equipment, net	5,051,972	4,930,217
Nonutility property, plant and equipment, less accumulated depreciation	6,949	6,953
Total property, plant and equipment, net	5,058,921	4,937,170
Investment in wholly-owned subsidiaries, at equity	0	0
Current assets
Cash and cash equivalents	52,169	47,360	11,022
Restricted cash	3,089	15,966
Advances to affiliates	0	0
Customer accounts receivable, net	186,859	147,832
Accrued unbilled revenues, net	129,155	101,036
Other accounts receivable, net	7,267	7,673
Fuel oil stock, at average cost	104,078	58,238
Materials and supplies, at average cost	71,877	67,344
Prepayments and other	46,031	44,083
Regulatory assets	66,664	30,435
Total current assets	667,189	519,967
Other long-term assets
Operating lease right-of-use-assets	101,470	127,654
Regulatory assets	498,879	736,273
Other	165,166	136,309
Total other long-term assets	765,515	1,000,236
Total assets	6,491,625	6,457,373
Capitalization
Common stock equity	2,261,899	2,141,918	2,047,352	1,957,641
Cumulative preferred stock–not subject to mandatory redemption	34,293	34,293
Long-term debt, net	1,624,427	1,561,302
Total capitalization	3,920,619	3,737,513
Current liabilities
Current portion of operating lease liabilities	49,368	64,730
Current portion of long-term debt, net	51,975	0
Short-term borrowings from non-affiliate	0	49,979
Short-term borrowings-affiliate	0	0
Accounts payable	160,007	133,849
Interest and dividends payable	17,325	20,350
Taxes accrued, including revenue taxes	208,280	192,524
Regulatory liabilities	29,760	37,301
Other	71,569	74,262
Total current liabilities	588,284	572,995
Deferred credits and other liabilities
Operating lease liabilities	65,780	69,494
Deferred income taxes	408,634	397,798
Regulatory liabilities	967,008	922,485
Unamortized tax credits	103,945	111,915
Defined benefit pension and other postretirement benefit plans liability	321,780	530,532
Other	115,575	114,641
Total deferred credits and other liabilities	1,982,722	2,146,865
Total capitalization and liabilities	6,491,625	6,457,373
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Hawaiian Electric (parent only)
Utility property, plant and equipment
Land	42,737	42,411
Plant and equipment	5,097,033	4,960,470
Less accumulated depreciation	(1,757,096)	(1,677,256)
Construction in progress	159,854	143,616
Utility property, plant and equipment, net	3,542,528	3,469,241
Nonutility property, plant and equipment, less accumulated depreciation	5,302	5,306
Total property, plant and equipment, net	3,547,830	3,474,547
Investment in wholly-owned subsidiaries, at equity	676,237	626,890
Current assets
Cash and cash equivalents	23,344	42,205	2,239
Restricted cash	3,089	15,966
Advances to affiliates	1,000	26,700
Customer accounts receivable, net	135,949	102,736
Accrued unbilled revenues, net	92,469	73,628
Other accounts receivable, net	18,624	17,984
Fuel oil stock, at average cost	71,184	38,777
Materials and supplies, at average cost	42,006	38,786
Prepayments and other	32,140	34,306
Regulatory assets	58,695	22,095
Total current assets	478,500	413,183
Other long-term assets
Operating lease right-of-use-assets	78,710	125,858
Regulatory assets	337,903	513,192
Other	130,546	98,307
Total other long-term assets	547,159	737,357
Total assets	5,249,726	5,251,977
Capitalization
Common stock equity	2,261,899	2,141,918	2,047,352	1,957,641
Cumulative preferred stock–not subject to mandatory redemption	22,293	22,293
Long-term debt, net	1,136,620	1,116,426
Total capitalization	3,420,812	3,280,637
Current liabilities
Current portion of operating lease liabilities	45,955	64,599
Current portion of long-term debt, net	39,981
Short-term borrowings from non-affiliate		49,979
Short-term borrowings-affiliate	0	0
Accounts payable	111,024	97,102
Interest and dividends payable	12,442	14,480
Taxes accrued, including revenue taxes	143,723	135,018
Regulatory liabilities	22,240	20,224
Other	56,752	57,926
Total current liabilities	432,117	439,328
Deferred credits and other liabilities
Operating lease liabilities	46,426	67,824
Deferred income taxes	291,027	282,685
Regulatory liabilities	695,152	656,270
Unamortized tax credits	76,201	82,563
Defined benefit pension and other postretirement benefit plans liability	220,480	373,112
Other	67,511	69,558
Total deferred credits and other liabilities	1,396,797	1,532,012
Total capitalization and liabilities	5,249,726	5,251,977
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Hawaii Electric Light
Utility property, plant and equipment
Land	5,606	5,606
Plant and equipment	1,390,361	1,352,885
Less accumulated depreciation	(619,991)	(597,606)
Construction in progress	17,129	13,043
Utility property, plant and equipment, net	793,105	773,928
Nonutility property, plant and equipment, less accumulated depreciation	115	115
Total property, plant and equipment, net	793,220	774,043
Investment in wholly-owned subsidiaries, at equity	0	0
Current assets
Cash and cash equivalents	5,326	3,046	6,885
Restricted cash	0	0
Advances to affiliates	0	0
Customer accounts receivable, net	28,469	23,989
Accrued unbilled revenues, net	19,529	13,631
Other accounts receivable, net	3,347	3,028
Fuel oil stock, at average cost	12,814	8,471
Materials and supplies, at average cost	9,727	9,896
Prepayments and other	6,052	5,197
Regulatory assets	3,051	1,954
Total current assets	88,315	69,212
Other long-term assets
Operating lease right-of-use-assets	22,442	1,443
Regulatory assets	81,645	114,461
Other	17,124	17,992
Total other long-term assets	121,211	133,896
Total assets	1,002,746	977,151
Capitalization
Common stock equity	332,900	317,451	298,998	295,874
Cumulative preferred stock–not subject to mandatory redemption	7,000	7,000
Long-term debt, net	234,390	216,447
Total capitalization	574,290	540,898
Current liabilities
Current portion of operating lease liabilities	3,378	98
Current portion of long-term debt, net	11,994
Short-term borrowings from non-affiliate		0
Short-term borrowings-affiliate	1,000	18,800
Accounts payable	26,139	19,570
Interest and dividends payable	2,617	3,138
Taxes accrued, including revenue taxes	33,153	29,869
Regulatory liabilities	3,247	8,785
Other	14,158	13,851
Total current liabilities	95,686	94,111
Deferred credits and other liabilities
Operating lease liabilities	19,063	1,344
Deferred income taxes	53,298	54,108
Regulatory liabilities	179,267	173,938
Unamortized tax credits	14,212	15,363
Defined benefit pension and other postretirement benefit plans liability	48,900	77,679
Other	18,030	19,710
Total deferred credits and other liabilities	332,770	342,142
Total capitalization and liabilities	1,002,746	977,151
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Maui Electric
Utility property, plant and equipment
Land	3,594	3,594
Plant and equipment	1,248,589	1,195,988
Less accumulated depreciation	(563,430)	(544,217)
Construction in progress	27,586	31,683
Utility property, plant and equipment, net	716,339	687,048
Nonutility property, plant and equipment, less accumulated depreciation	1,532	1,532
Total property, plant and equipment, net	717,871	688,580
Investment in wholly-owned subsidiaries, at equity	0	0
Current assets
Cash and cash equivalents	23,422	2,032	1,797
Restricted cash	0	0
Advances to affiliates	0	0
Customer accounts receivable, net	22,441	21,107
Accrued unbilled revenues, net	17,157	13,777
Other accounts receivable, net	3,031	2,856
Fuel oil stock, at average cost	20,080	10,990
Materials and supplies, at average cost	20,144	18,662
Prepayments and other	7,114	4,580
Regulatory assets	4,918	6,386
Total current assets	118,307	80,390
Other long-term assets
Operating lease right-of-use-assets	318	353
Regulatory assets	79,331	108,620
Other	18,510	20,010
Total other long-term assets	98,159	128,983
Total assets	934,337	897,953
Capitalization
Common stock equity	343,260	309,363	292,870	280,863
Cumulative preferred stock–not subject to mandatory redemption	5,000	5,000
Long-term debt, net	253,417	228,429
Total capitalization	601,677	542,792
Current liabilities
Current portion of operating lease liabilities	35	33
Current portion of long-term debt, net	0
Short-term borrowings from non-affiliate		0
Short-term borrowings-affiliate	0	7,900
Accounts payable	22,844	17,177
Interest and dividends payable	2,269	2,790
Taxes accrued, including revenue taxes	30,679	27,637
Regulatory liabilities	4,273	8,292
Other	18,540	18,621
Total current liabilities	78,640	82,450
Deferred credits and other liabilities
Operating lease liabilities	291	326
Deferred income taxes	64,309	61,005
Regulatory liabilities	92,589	92,277
Unamortized tax credits	13,532	13,989
Defined benefit pension and other postretirement benefit plans liability	53,257	79,741
Other	30,042	25,373
Total deferred credits and other liabilities	254,020	272,711
Total capitalization and liabilities	934,337	897,953
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Other subsidiaries
Utility property, plant and equipment
Land	0	0
Plant and equipment	0	0
Less accumulated depreciation	0	0
Construction in progress	0	0
Utility property, plant and equipment, net	0	0
Nonutility property, plant and equipment, less accumulated depreciation	0	0
Total property, plant and equipment, net	0	0
Investment in wholly-owned subsidiaries, at equity	0	0
Current assets
Cash and cash equivalents	77	77	101
Restricted cash	0	0
Advances to affiliates	0	0
Customer accounts receivable, net	0	0
Accrued unbilled revenues, net	0	0
Other accounts receivable, net	0	0
Fuel oil stock, at average cost	0	0
Materials and supplies, at average cost	0	0
Prepayments and other	0	0
Regulatory assets	0	0
Total current assets	77	77
Other long-term assets
Operating lease right-of-use-assets	0	0
Regulatory assets	0	0
Other	0	0
Total other long-term assets	0	0
Total assets	77	77
Capitalization
Common stock equity	77	77	101	101
Cumulative preferred stock–not subject to mandatory redemption	0	0
Long-term debt, net	0	0
Total capitalization	77	77
Current liabilities
Current portion of operating lease liabilities	0	0
Current portion of long-term debt, net	0
Short-term borrowings from non-affiliate		0
Short-term borrowings-affiliate	0	0
Accounts payable	0	0
Interest and dividends payable	0	0
Taxes accrued, including revenue taxes	0	0
Regulatory liabilities	0	0
Other	0	0
Total current liabilities	0	0
Deferred credits and other liabilities
Operating lease liabilities	0	0
Deferred income taxes	0	0
Regulatory liabilities	0	0
Unamortized tax credits	0	0
Defined benefit pension and other postretirement benefit plans liability	0	0
Other	0	0
Total deferred credits and other liabilities	0	0
Total capitalization and liabilities	77	77
Hawaiian Electric Company, Inc. and Subsidiaries | Consolidating adjustments
Utility property, plant and equipment
Land	0	0
Plant and equipment	0	0
Less accumulated depreciation	0	0
Construction in progress	0	0
Utility property, plant and equipment, net	0	0
Nonutility property, plant and equipment, less accumulated depreciation	0	0
Total property, plant and equipment, net	0	0
Investment in wholly-owned subsidiaries, at equity	(676,237)	(626,890)
Current assets
Cash and cash equivalents	0	0	0
Restricted cash	0	0
Advances to affiliates	(1,000)	(26,700)
Customer accounts receivable, net	0	0
Accrued unbilled revenues, net	0	0
Other accounts receivable, net	(17,735)	(16,195)
Fuel oil stock, at average cost	0	0
Materials and supplies, at average cost	0	0
Prepayments and other	725	0
Regulatory assets	0	0
Total current assets	(18,010)	(42,895)
Other long-term assets
Operating lease right-of-use-assets	0	0
Regulatory assets	0	0
Other	(1,014)	0
Total other long-term assets	(1,014)	0
Total assets	(695,261)	(669,785)
Capitalization
Common stock equity	(676,237)	(626,891)	$ (591,969)	$ (576,838)
Cumulative preferred stock–not subject to mandatory redemption	0	0
Long-term debt, net	0	0
Total capitalization	(676,237)	(626,891)
Current liabilities
Current portion of operating lease liabilities	0	0
Current portion of long-term debt, net	0
Short-term borrowings from non-affiliate		0
Short-term borrowings-affiliate	(1,000)	(26,700)
Accounts payable	0	0
Interest and dividends payable	(3)	(58)
Taxes accrued, including revenue taxes	725	0
Regulatory liabilities	0	0
Other	(17,881)	(16,136)
Total current liabilities	(18,159)	(42,894)
Deferred credits and other liabilities
Operating lease liabilities	0	0
Deferred income taxes	0	0
Regulatory liabilities	0	0
Unamortized tax credits	0	0
Defined benefit pension and other postretirement benefit plans liability	(857)	0
Other	(8)	0
Total deferred credits and other liabilities	(865)	0
Total capitalization and liabilities	$ (695,261)	$ (669,785)