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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Face (par) amount of the original debt instrument that was repurchased.

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Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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No definition available.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt.

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The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt.

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Long-term debt (Details) - USD ($)				12 Months Ended
Long-term debt (Details) - USD ($)	Nov. 20, 2017	Oct. 06, 2017	Jun. 29, 2017	Dec. 31, 2017	Dec. 26, 2017	Dec. 14, 2017	Dec. 31, 2016
Long-term debt
Long-term debt, net—other than bank				$ 1,683,797,000			$ 1,619,019,000
Less unamortized debt issuance costs				(2,007,000)			(241,000)
Aggregate principal payments
2018				54,000,000
2019				4,000,000
2020				100,000,000
2021				54,000,000
2022				206,000,000
Electric utility
Aggregate principal payments
2018				50,000,000
2019				0
2020				96,000,000
2021				0
2022				$ 52,000,000
Senior notes \| Hamakua Energy Partners, L.P. (HEP)
Long-term debt
Debt instrument, stated interest rate					4.02%
Aggregate principal payments
Debt instrument, face amount					$ 67,300,000
Term loan \| Hamakua Energy Partners, L.P. (HEP)
Long-term debt
Debt instrument, stated interest rate				4.02%
Special purpose revenue bonds issued on behalf of electric utility subsidiaries
Long-term debt
Long-term debt, net—other than bank				$ 1,368,479,000			1,319,260,000
Hamakua Energy, LLC Loan at 4.02% Due 2030 \| Senior notes
Long-term debt
Gross long-term debt				$ 67,325,000			0
Debt instrument, stated interest rate				4.02%
Senior Notes 2.99% Due 2022 \| Senior notes
Long-term debt
Gross long-term debt				$ 150,000,000			0
Senior Notes 2.99% Due 2022 \| Term loan
Long-term debt
Debt instrument, stated interest rate				2.99%
HEI 5.67% senior notes, due 2021 \| Senior notes
Long-term debt
Gross long-term debt				$ 50,000,000			50,000,000
Debt instrument, stated interest rate				5.67%
HEI 3.99% senior notes, due 2023 \| Senior notes
Long-term debt
Gross long-term debt				$ 50,000,000			50,000,000
Debt instrument, stated interest rate				3.99%
HEI Term loans (LIBOR 0.75%), paid in 2017
Aggregate principal payments
Aggregate repurchased principal amount	$ 75,000,000
HEI Term loans (LIBOR 0.75%), paid in 2017 \| Term loan
Long-term debt
Gross long-term debt				$ 0			$ 200,000,000
HEI Term loans (LIBOR 0.75%), paid in 2017 \| Term loan \| LIBOR
Long-term debt
Line of credit facility basis point spread				0.00%
Eurodollar Term Loan \| Unsecured Debt
Aggregate principal payments
Proceeds from issuance of debt		$ 125,000,000
Debt instrument term		364 days
Aggregate repurchased principal amount		$ 125,000,000
Debt instrument, face amount	125,000,000
Repayments of unsecured debt	$ 75,000,000
Refunding Series 2007B Special Purpose Revenue Bonds
Long-term debt
Debt instrument, stated interest rate				4.60%
Refunding Series 2007B Special Purpose Revenue Bonds \| Unsecured Debt
Long-term debt
Debt instrument, stated interest rate			4.60%
Aggregate principal payments
Aggregate repurchased principal amount			$ 125,000,000
Bank of America Loan Agreement
Long-term debt
Debt instrument, stated interest rate	2.99%
Aggregate principal payments
Debt instrument, face amount	$ 150,000,000
Refunding Series 2017A Special Purpose Revenue Bonds \| Unsecured Debt
Long-term debt
Debt instrument, stated interest rate			3.10%
Aggregate principal payments
Debt instrument, face amount			$ 125,000,000
Refunding Series 2017A Special Purpose Revenue Bonds \| Unsecured Debt \| Hawaiian Electric Company, Inc (HECO)
Aggregate principal payments
Proceeds from issuance of debt			62,000,000
Refunding Series 2017A Special Purpose Revenue Bonds \| Unsecured Debt \| HELCO
Aggregate principal payments
Proceeds from issuance of debt			8,000,000
Refunding Series 2017A Special Purpose Revenue Bonds \| Unsecured Debt \| MECO
Aggregate principal payments
Proceeds from issuance of debt			$ 55,000,000
Refunding Series 2017B Special Purpose Revenue Bonds \| Unsecured Debt
Long-term debt
Debt instrument, stated interest rate			4.00%
Aggregate principal payments
Debt instrument, face amount			$ 140,000,000
Refunding Series 2017B Special Purpose Revenue Bonds \| Unsecured Debt \| Hawaiian Electric Company, Inc (HECO)
Aggregate principal payments
Proceeds from issuance of debt			100,000,000
Refunding Series 2017B Special Purpose Revenue Bonds \| Unsecured Debt \| HELCO
Aggregate principal payments
Proceeds from issuance of debt			20,000,000
Refunding Series 2017B Special Purpose Revenue Bonds \| Unsecured Debt \| MECO
Aggregate principal payments
Proceeds from issuance of debt			$ 20,000,000
Series 2007A Special Purpose Revenue Bonds \| Unsecured Debt
Long-term debt
Debt instrument, stated interest rate			4.65%
Aggregate principal payments
Aggregate repurchased principal amount			$ 140,000,000
4.31%, Series 2017A, due 2047
Long-term debt
Debt instrument, stated interest rate				4.31%
4.31%, Series 2017A, due 2047 \| Electric utility
Long-term debt
Debt instrument, stated interest rate						4.31%
Aggregate principal payments
Debt instrument, face amount						$ 40,000,000
4.31%, Series 2017A, due 2047 \| MECO
Aggregate principal payments
Debt instrument, face amount						$ 10,000,000