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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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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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The cash inflow from an entity that is affiliated with the entity by means of direct or indirect ownership.

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Long-term debt (Details) - USD ($)	1 Months Ended
Long-term debt (Details) - USD ($)	Dec. 31, 2018	Jun. 30, 2018	Oct. 04, 2018	May 30, 2018	Dec. 31, 2017
Long-term debt
Less unamortized debt issuance costs	$ (2,599,000)				$ (2,007,000)
Long-term debt, net—other than bank	1,879,641,000				1,683,797,000
Aggregate principal payments
2019	4,000,000
2020	100,000,000
2021	54,000,000
2022	206,000,000
2023	154,000,000
Contribution to maintain targeted equity capitalization structure	71,000,000
Electric utility
Aggregate principal payments
2019	0
2020	96,000,000
2021	0
2022	52,000,000
2023	100,000,000
Hawaiian Electric Company, Inc. and Subsidiaries
Long-term debt
Gross long-term debt	1,426,546,000				1,376,546,000
Unsecured Debt
Aggregate principal payments
Debt instrument, face amount			$ 150,000,000
Unsecured Debt \| Mauo, LLC
Long-term debt
Gross long-term debt	0
Aggregate principal payments
Debt instrument, face amount		$ 50,500,000.0
Unsecured Debt \| Mauo, LLC \| LIBOR
Aggregate principal payments
Line of credit facility basis point spread		1.375%
Special purpose revenue bonds issued on behalf of electric utility subsidiaries
Long-term debt
Gross long-term debt	1,418,802,000				1,368,479,000
Hamakua Energy 4.02% notes, due 2030 \| Senior notes
Long-term debt
Gross long-term debt	$ 63,438,000				67,325,000
Debt instrument, stated interest rate	4.02%
HEI 2.99% term loan, due 2022 \| Senior notes
Long-term debt
Gross long-term debt	$ 150,000,000				150,000,000
HEI 2.99% term loan, 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 4.58% senior notes, due 2025 \| Senior notes
Long-term debt
Debt instrument, stated interest rate	4.58%
HEI 4.58% senior notes, due 2025 \| Term loan
Long-term debt
Gross long-term debt	$ 50,000,000				0
HEI 4.72% senior notes, due 2028 \| Senior notes
Long-term debt
Debt instrument, stated interest rate	4.72%
HEI 4.72% senior notes, due 2028 \| Term loan
Long-term debt
Gross long-term debt	$ 100,000,000				$ 0
HEI Series 2018A
Long-term debt
Debt instrument, stated interest rate			4.58%
Aggregate principal payments
Debt instrument, face amount			$ 50,000,000
HEI Series 2018A \| Unsecured Debt
Long-term debt
Gross long-term debt				$ 67,500,000
Debt instrument, stated interest rate				4.38%
HEI Series 2018A \| Unsecured Debt \| Hawaiian Electric Company, Inc. and Subsidiaries
Long-term debt
Gross long-term debt				$ 52,000,000
HEI Series 2018A \| Unsecured Debt \| HELCO
Long-term debt
Gross long-term debt				9,000,000
HEI Series 2018A \| Unsecured Debt \| MECO
Long-term debt
Gross long-term debt				6,500,000
HEI Series 2018B
Long-term debt
Debt instrument, stated interest rate			4.72%
Aggregate principal payments
Debt instrument, face amount			$ 100,000,000
HEI Series 2018B \| Unsecured Debt
Long-term debt
Gross long-term debt				$ 17,500,000
Debt instrument, stated interest rate				4.53%
HEI Series 2018B \| Unsecured Debt \| Hawaiian Electric Company, Inc. and Subsidiaries
Long-term debt
Gross long-term debt				$ 12,500,000
HEI Series 2018B \| Unsecured Debt \| HELCO
Long-term debt
Gross long-term debt				3,000,000
HEI Series 2018B \| Unsecured Debt \| MECO
Long-term debt
Gross long-term debt				2,000,000
Series 2018C \| Unsecured Debt
Long-term debt
Gross long-term debt				$ 15,000,000
Debt instrument, stated interest rate				4.72%
Series 2018C \| Unsecured Debt \| Hawaiian Electric Company, Inc. and Subsidiaries
Long-term debt
Gross long-term debt				$ 10,500,000
Series 2018C \| Unsecured Debt \| HELCO
Long-term debt
Gross long-term debt				3,000,000
Series 2018C \| Unsecured Debt \| MECO
Long-term debt
Gross long-term debt				$ 1,500,000