Fair value measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financial assets
Available-for-sale investment securities, at fair value	$ 785,837	$ 550,394
Financial liabilities
Short-term borrowings—other than bank	171,992	118,972
Other bank borrowings	368,593	290,656
Carrying or notional amount
Financial assets
Money market funds	10	10
Available-for-sale investment securities, at fair value	785,837	550,394
Stock in Federal Home Loan Bank	10,678	69,302
Loans receivable, net	4,492,728	4,397,457
Derivative assets	586	398
Financial liabilities
Deposit liabilities	4,825,954	4,623,415
Short-term borrowings—other than bank	171,992	118,972
Other bank borrowings	368,593	290,656
Long-term debt, net—other than bank	1,506,546	1,506,546
Derivative liabilities	125	114
Carrying or notional amount | American Savings Bank (ASB)
Financial liabilities
Notional amount of loans serviced	1,600,000	1,400,000
Estimated fair value
Financial assets
Money market funds	10	10
Available-for-sale investment securities, at fair value	785,837	550,394
Stock in Federal Home Loan Bank	10,678	69,302
Loans receivable, net	4,700,042	4,578,822
Derivative assets	586	398
Financial liabilities
Deposit liabilities	4,828,402	4,623,773
Short-term borrowings—other than bank	171,992	118,972
Other bank borrowings	375,428	298,837
Long-term debt, net—other than bank	1,595,161	1,622,736
Derivative liabilities	125	114
Estimated fair value | Level 1
Financial assets
Derivative assets	0	0
Financial liabilities
Derivative liabilities	112	71
Estimated fair value | Level 2
Financial assets
Money market funds	10	10
Available-for-sale investment securities, at fair value	785,837	550,394
Stock in Federal Home Loan Bank	10,678	69,302
Derivative assets	586	398
Financial liabilities
Deposit liabilities	4,828,402	4,623,773
Short-term borrowings—other than bank	171,992	118,972
Other bank borrowings	375,428	298,837
Long-term debt, net—other than bank	1,595,161	1,622,736
Derivative liabilities	13	43
Estimated fair value | Level 3
Financial assets
Loans receivable, net	4,700,042	4,578,822
Estimated fair value | American Savings Bank (ASB)
Financial liabilities
Servicing rights on loans	16,000	14,500
Hawaiian Electric Company | Carrying or notional amount
Financial liabilities
The Utilities’ short-term borrowings (included in amount above)	94,995
Long-term debt, net—other than bank	1,206,546	1,206,546
Hawaiian Electric Company | Estimated fair value
Financial liabilities
The Utilities’ short-term borrowings (included in amount above)	94,995
Long-term debt, net—other than bank	1,288,112	1,313,893
Hawaiian Electric Company | Estimated fair value | Level 2
Financial liabilities
The Utilities’ short-term borrowings (included in amount above)	94,995
Long-term debt, net—other than bank	$ 1,288,112	$ 1,313,893