Income taxes - Deferred Tax Assets and Liabilities Due to Book/Tax Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets
Regulatory liabilities, excluding amounts attributable to property, plant and equipment	$ 87,817	$ 93,684
Operating lease liabilities	35,449	41,582
Revenue taxes	35,040	22,726
Allowance for bad debts	26,217	31,973
Other	58,518	44,127
Total deferred tax assets	243,041	234,092
Deferred tax liabilities
Property, plant and equipment related	500,659	487,209
Operating lease right-of-use assets	35,271	41,370
Regulatory assets, excluding amounts attributable to property, plant and equipment	23,700	25,841
Retirement benefits	6,863	18,407
Other	61,308	56,354
Total deferred tax liabilities	627,801	629,181
Net deferred income tax liability	384,760	395,089
Deferred tax assets, tax credit carryforwards	11,000
Hawaiian Electric Company, Inc. and Subsidiaries
Deferred tax assets
Regulatory liabilities, excluding amounts attributable to property, plant and equipment	87,817	93,684
Operating lease liabilities	29,661	34,586
Revenue taxes	35,040	22,726
Allowance for bad debts	7,156	4,835
Other	20,529	24,741
Total deferred tax assets	180,203	180,572
Deferred tax liabilities
Property, plant and equipment related	490,713	473,734
Operating lease right-of-use assets	29,661	34,586
Regulatory assets, excluding amounts attributable to property, plant and equipment	23,700	25,841
Retirement benefits	8,261	20,537
Other	36,502	23,672
Total deferred tax liabilities	588,837	578,370
Net deferred income tax liability	408,634	$ 397,798
Deferred tax assets, tax credit carryforwards	2,500
State and Local Jurisdiction
Deferred tax liabilities
Tax credit carryforward	14,600
State and Local Jurisdiction | Hawaiian Electric Company, Inc. and Subsidiaries
Deferred tax liabilities
Tax credit carryforward	$ 3,400