Fair value measurements (Details) (USD $)	Sep. 30, 2011	Dec. 31, 2010
Financial liabilities
Short-term borrowings-other than bank	$ 51,195,000	$ 24,923,000
Other bank borrowings	237,934,000	237,319,000
Hawaiian Electric Company, Inc. and Subsidiaries \| Carrying or notional amount
Financial assets
Cash and cash equivalents, excluding money market funds	13,869,000	122,936,000
Financial liabilities
Long-term debt, net-other than bank	1,058,038,000	1,057,942,000
Off-balance sheet items
HECO-obligated preferred securities of trust subsidiary	50,000,000	50,000,000
American Savings Bank (ASB) \| Carrying or notional amount
Off-balance sheet items
Loan commitments and unused lines and letters of credit	1,400,000,000	1,200,000,000
Notional amount of loan serviced	886,000,000	818,000,000
Carrying or notional amount
Financial assets
Cash and cash equivalents, excluding money market funds	283,473,000	329,553,000
Money market funds	10,000	1,098,000
Available-for-sale investment and mortgage-related securities	571,045,000	678,152,000
Investment in stock of Federal Home Loan Bank of Seattle	97,764,000	97,764,000
Loans receivable, net	3,647,197,000	3,497,729,000
Financial liabilities
Deposit liabilities	4,062,801,000	3,975,372,000
Short-term borrowings-other than bank	51,195,000	24,923,000
Other bank borrowings	237,934,000	237,319,000
Long-term debt, net-other than bank	1,340,038,000	1,364,942,000
Forward starting swaps		2,762,000
Hawaiian Electric Company, Inc. and Subsidiaries \| Estimated fair value
Financial assets
Cash and cash equivalents, excluding money market funds	13,869,000	122,936,000
Financial liabilities
Long-term debt, net-other than bank	1,033,222,000	1,020,550,000
Off-balance sheet items
HECO-obligated preferred securities of trust subsidiary	51,960,000	52,500,000
American Savings Bank (ASB) \| Estimated fair value
Off-balance sheet items
Loan commitments and unused lines and letters of credit	1,100,000	400,000
Servicing rights on loans	7,700,000	8,800,000
Estimated fair value
Financial assets
Cash and cash equivalents, excluding money market funds	283,473,000	329,553,000
Money market funds	10,000	1,098,000
Available-for-sale investment and mortgage-related securities	571,045,000	678,152,000
Investment in stock of Federal Home Loan Bank of Seattle	97,764,000	97,764,000
Loans receivable, net	3,850,247,000	3,639,983,000
Financial liabilities
Deposit liabilities	4,069,420,000	3,979,027,000
Short-term borrowings-other than bank	51,195,000	24,923,000
Other bank borrowings	255,751,000	251,822,000
Long-term debt, net-other than bank	1,342,518,000	1,345,770,000
Forward starting swaps		$ 2,762,000

The fair value of financial commitments, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

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The carrying value of other bank borrowings as of the balance sheet date, including securities sold under agreements to repurchase and advances from the Federal Home Loan Bank.

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The fair value of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

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Fair value as of the balance sheet date of all interest rate derivative liabilities designated as cash flow hedging instruments.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Sum of the carrying amounts at the balance sheet date of short-term borrowings not otherwise specified in the taxonomy having initial terms less than one year or the normal operating cycle, if longer.

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Fair value as of the balance sheet date of an asset representing net future revenues from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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