Fair value measurements - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financial assets
Available-for-sale investment securities	$ 1,105,182	$ 820,648
Financial liabilities
Short-term borrowings—other than bank	0	103,063
Other bank borrowings	192,618	328,582
Carrying or notional amount
Financial assets
Money market funds	13,085	10
Available-for-sale investment securities	1,105,182	820,648
Stock in Federal Home Loan Bank	11,218	10,678
Loans receivable, net	4,701,977	4,570,412
Mortgage servicing rights	9,373	8,884
Bank-owned life insurance	143,197	138,139
Derivative assets	23,578	22,616
Financial liabilities
Deposit liabilities	5,548,929	5,025,254
Short-term borrowings—other than bank		103,063
Other bank borrowings	192,618	328,582
Long-term debt, net—other than bank	1,619,019	1,578,368
Derivative liabilities	53,852	23,269
Estimated fair value
Financial assets
Money market funds	13,085	10
Available-for-sale investment securities	1,105,182	820,648
Stock in Federal Home Loan Bank	11,218	10,678
Loans receivable, net	4,852,826	4,749,525
Mortgage servicing rights	13,216	11,790
Bank-owned life insurance	143,197	138,139
Derivative assets	453	385
Financial liabilities
Deposit liabilities	5,546,644	5,024,500
Short-term borrowings—other than bank		103,063
Other bank borrowings	193,991	333,392
Long-term debt, net—other than bank	1,704,717	1,669,087
Derivative liabilities	952	30
Estimated fair value | Level 1
Financial assets
Money market funds	0	0
Available-for-sale investment securities	0	0
Stock in Federal Home Loan Bank	0	0
Loans receivable, net	0	0
Mortgage servicing rights	0	0
Bank-owned life insurance	0	0
Derivative assets	0	0
Financial liabilities
Deposit liabilities	0	0
Short-term borrowings—other than bank		0
Other bank borrowings	0	0
Long-term debt, net—other than bank	0	0
Derivative liabilities	129	15
Estimated fair value | Level 2
Financial assets
Money market funds	13,085	10
Available-for-sale investment securities	1,089,755	820,648
Stock in Federal Home Loan Bank	11,218	10,678
Loans receivable, net	13,333	4,639
Mortgage servicing rights	0	0
Bank-owned life insurance	143,197	138,139
Derivative assets	453	385
Financial liabilities
Deposit liabilities	5,546,644	5,024,500
Short-term borrowings—other than bank		103,063
Other bank borrowings	193,991	333,392
Long-term debt, net—other than bank	1,704,717	1,669,087
Derivative liabilities	823	15
Estimated fair value | Level 3
Financial assets
Money market funds	0	0
Available-for-sale investment securities	15,427	0
Stock in Federal Home Loan Bank	0	0
Loans receivable, net	4,839,493	4,744,886
Mortgage servicing rights	13,216	11,790
Bank-owned life insurance	0	0
Derivative assets	0	0
Financial liabilities
Deposit liabilities	0	0
Short-term borrowings—other than bank		0
Other bank borrowings	0	0
Long-term debt, net—other than bank	0	0
Derivative liabilities	0	0
Hawaiian Electric Company, Inc. and Subsidiaries | Carrying or notional amount
Financial liabilities
Long-term debt, net—other than bank	1,319,260	1,278,702
Derivative liabilities	20,734
Hawaiian Electric Company, Inc. and Subsidiaries | Estimated fair value
Financial liabilities
Long-term debt, net—other than bank	1,399,490	1,363,766
Derivative liabilities	743
Hawaiian Electric Company, Inc. and Subsidiaries | Estimated fair value | Level 1
Financial liabilities
Long-term debt, net—other than bank	0	0
Derivative liabilities	0
Hawaiian Electric Company, Inc. and Subsidiaries | Estimated fair value | Level 2
Financial liabilities
Long-term debt, net—other than bank	1,399,490	1,363,766
Derivative liabilities	743
Hawaiian Electric Company, Inc. and Subsidiaries | Estimated fair value | Level 3
Financial liabilities
Long-term debt, net—other than bank	0	$ 0
Derivative liabilities	$ 0