Fair value measurements (Details) - HECO (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Carrying or notional amount
Financial liabilities
Long-term debt, net, including amounts due within one year (Level 2)	$ 1,422,872	$ 1,340,070
Carrying or notional amount | Hawaiian Electric Company, Inc. and Subsidiaries | Fair value measurements on a recurring basis
Financial liabilities
Long-term debt, net, including amounts due within one year (Level 2)	1,147,872	1,058,070
Estimated fair value
Financial liabilities
Long-term debt, net, including amounts due within one year (Level 2)	1,481,004	1,400,241
Estimated fair value | Hawaiian Electric Company, Inc. and Subsidiaries | Fair value measurements on a recurring basis
Financial liabilities
Long-term debt, net, including amounts due within one year (Level 2)	$ 1,181,631	$ 1,095,133