Fair value measurements (Details) (USD $)	Mar. 31, 2012	Dec. 31, 2011
Financial liabilities
Short-term borrowings-other than bank	$ 156,288,000	$ 68,821,000
Other bank borrowings	232,843,000	233,229,000
Carrying or notional amount | Significant other observable inputs (Level 2)
Financial assets
Cash and cash equivalents, excluding money market funds	236,336,000	270,255,000
Money market funds	10,000	10,000
Available-for-sale investment and mortgage-related securities	631,063,000	624,331,000
Investment in stock of Federal Home Loan Bank of Seattle	97,764,000	97,764,000
Financial liabilities
Deposit liabilities	4,125,204,000	4,070,032,000
Short-term borrowings-other than bank	156,288,000	68,821,000
Other bank borrowings	232,843,000	233,229,000
Long-term debt, net-other than bank	1,282,602,000	1,340,070,000
Carrying or notional amount | Significant Unobservable inputs (Level 3)
Financial assets
Loans receivable, net	3,687,058,000	3,652,419,000
Carrying or notional amount | Hawaiian Electric Company, Inc. and Subsidiaries | Significant other observable inputs (Level 2)
Off-balance sheet items
HECO-obligated preferred securities of trust subsidiary	50,000,000	50,000,000
Carrying or notional amount | American Savings Bank (ASB)
Off-balance sheet items
Loan commitments and unused lines and letters of credit	1,400,000,000	1,300,000,000
Notional amount of loans serviced	1,000,000,000	993,000,000
Estimated fair value | Significant other observable inputs (Level 2)
Financial assets
Cash and cash equivalents, excluding money market funds	236,336,000	270,255,000
Money market funds	10,000	10,000
Available-for-sale investment and mortgage-related securities	631,063,000	624,331,000
Investment in stock of Federal Home Loan Bank of Seattle	97,764,000	97,764,000
Financial liabilities
Deposit liabilities	4,130,996,000	4,075,656,000
Short-term borrowings-other than bank	156,288,000	68,821,000
Other bank borrowings	249,259,000	250,486,000
Long-term debt, net-other than bank	1,338,777,000	1,400,241,000
Estimated fair value | Significant other observable inputs (Level 2) | Error correction in estimated fair value
Financial liabilities
Increase in deposit liabilities		83,900,000
Estimated fair value | Significant Unobservable inputs (Level 3)
Financial assets
Loans receivable, net	3,896,679,000	3,886,253,000
Estimated fair value | Hawaiian Electric Company, Inc. and Subsidiaries | Significant other observable inputs (Level 2)
Off-balance sheet items
HECO-obligated preferred securities of trust subsidiary	50,000,000	50,000,000
Estimated fair value | American Savings Bank (ASB)
Off-balance sheet items
Loan commitments and unused lines and letters of credit	600,000	300,000
Servicing rights on loans	$ 10,000,000	$ 9,800,000