Credit agreement and long-term debt (Details) (USD $)								0 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2013 Hawaiian Electric Industries, Inc. Minimum	Mar. 31, 2013 Hawaiian Electric Industries, Inc. Maximum	Mar. 31, 2013 Line of credit facility item	Mar. 06, 2013 Series 2013A Senior note 3.99%, due 2023	Mar. 07, 2013 HEI medium-term note 5.25%, due 2013	Mar. 31, 2013 HEI medium-term note 5.25%, due 2013
Credit agreement
Revolving noncollateralized credit facility with a letter of credit sub-facility							$ 125,000,000
Number of financial institutions							8
Changes in long-term debt
Notes issued through private placement								50,000,000
Debt instrument, stated interest rate (as a percent)								3.99%		5.25%
Consolidated net worth	1,607,265,000	1,593,865,000	1,550,855,000	1,528,706,000	975,000,000
Capitalization ratio required to be maintained as per the debt covenant (as a percent)						50.00%
Refinancing of unsecured debt payable									$ 50,000,000