Fair value measurements - (Details) - HECO (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Hawaiian Electric Company, Inc. and Subsidiaries \| Carrying or notional amount
Financial assets
Cash and cash equivalents, excluding money market accounts	$ 844	$ 122,936
Financial liabilities
Long-term debt, net-other than bank	1,058,006	1,057,942
Off-balance sheet items
HECO-obligated preferred securities of trust subsidiary	50,000	50,000
Hawaiian Electric Company, Inc. and Subsidiaries \| Carrying or notional amount \| Fair value measurements on a recurring basis \| Significant other observable inputs (Level 2)
Financial assets
Money market accounts	24,690
Carrying or notional amount
Financial assets
Cash and cash equivalents, excluding money market accounts	180,900	329,553
Money market accounts	85,846	1,098
Financial liabilities
Long-term debt, net-other than bank	1,440,006	1,364,942
Hawaiian Electric Company, Inc. and Subsidiaries \| Estimated fair value
Financial assets
Cash and cash equivalents, excluding money market accounts	844	122,936
Financial liabilities
Long-term debt, net-other than bank	1,004,669	1,020,550
Off-balance sheet items
HECO-obligated preferred securities of trust subsidiary	50,040	52,500
Hawaiian Electric Company, Inc. and Subsidiaries \| Estimated fair value \| Fair value measurements on a recurring basis \| Significant other observable inputs (Level 2)
Financial assets
Money market accounts	24,690
Estimated fair value
Financial assets
Cash and cash equivalents, excluding money market accounts	180,900	329,553
Money market accounts	85,846	1,098
Financial liabilities
Long-term debt, net-other than bank	$ 1,411,318	$ 1,345,770

This element represents the portion of the balance sheet assertion valued at fair value by the entity 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. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

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Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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