Electric utility subsidiary (Details 4) (USD $)	12 Months Ended		1 Months Ended						12 Months Ended					1 Months Ended	12 Months Ended			3 Months Ended			1 Months Ended	12 Months Ended		12 Months Ended
	Dec. 31, 2011 EGU Y extension	Dec. 31, 2011 Electric utility	Nov. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries	Jul. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries mW	Jan. 31, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Y	Aug. 31, 2010 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2009 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2009 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2013 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2012 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2011 Hawaiian Electric Company, Inc. and Subsidiaries mW agreement	Dec. 31, 2010 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2009 Hawaiian Electric Company, Inc. and Subsidiaries	Jan. 31, 2011 Hawaii Electric Light Company, Inc. (HELCO) gallons Y	Dec. 31, 2011 Campbell Industrial Park 110MW combustion turbine and transmission line Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2011 East Oahu transmission project	Dec. 31, 2011 East Oahu Transmission Project Phase 1	Dec. 31, 2010 East Oahu Transmission Project Phase 1 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2011 East Oahu Transmission Project Phase 1 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2011 East Oahu Transmission Project Phase 2	Apr. 30, 2010 East Oahu Transmission Project Phase 2 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2011 East Oahu Transmission Project Phase 2 Hawaiian Electric Company, Inc. and Subsidiaries	Jun. 30, 2011 East Oahu Transmission Project Phase 2 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2005 Customer Information System Project Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2011 Customer Information System Project Hawaiian Electric Company, Inc. and Subsidiaries
Fuel contracts
Estimated cost of minimum purchase within 2012 year											$ 1,000,000,000
Estimated cost of minimum purchase in 2013 year											500,000,000
Estimated cost of minimum purchase in 2014 year											300,000,000
Cost of purchases											1,300,000,000	1,000,000,000	700,000,000
Aina Koa Pono-Ka'u LLC
Contract term (in years)														20
Biodiesel contract supply amount per year (in gallons)														16,000,000
Power purchase agreements
Number of power purchase agreements (PPAs)											6
Power purchase capacity excluding agreements with smaller IPPs (in megawatts)											548
Purchases from IPPs including other smaller IPPs	690,000,000										689,652,000	548,800,000	499,804,000
Expected fixed capacity charges per year for 2012 through 2016, minimum											100,000,000
Expected fixed capacity charges from 2017 through 2030											600,000,000
Deferred cost to be recovered subject to PUC approval							3,900,000
Rate base increase for EOTP Phase I settlement agreement											31,000,000
Integration from renewable energy sources (in megawatts)				200
Deferred cost to be recovered for additional studies subject to PUC approval			600,000
Revenue recognized with respect to interim rate increase order											40,000,000
Estimated project cost above PUC approval															32,000,000				43,000,000
Cost of project recoverable from increase in annual revenue															163,000,000
Estimated cost of project upon completion																56,000,000	42,000,000			14,000,000
Project cost incurred															195,000,000
Estimated project cost subject to decision and order issued																			16,000,000
Amount authorized for the project																								20,000,000
Net estimated cost of using smart grid technology																					10,000,000
Estimated cost of smart grid technology																					15,000,000	11,000,000
Estimated statutory funding for smart grid technology																					5,000,000	3,000,000
Accumulated project cost																			59,000,000				8,000,000
Accumulated project planning and permitting cost																			12,000,000
Accumulated project planning and permitting cost after denial of permit																			24,000,000
Accumulated cost for allowance for funds used during construction															9,000,000				23,000,000
Capital and deferred costs authorized																								18,000,000
Deferred and capital cost estimate																									57,000,000
Deferred and capital cost recorded																									43,000,000
Gross plant cost agreed to be written-off in lieu of regulatory audit																			9,500,000
After-tax charge to net income due to settlement agreement																		6,000,000
Estimated interim increase agreed to be stipulated, subject to PUC approval, based on additional revenue requirements																			5,000,000
Increase to rate base																			31,000,000
Environmental regulation
Number of periods allowed for compliance of EPA regulation (in years)	8
Number of EGUs impacted by proposed rules of MACT	14
Number of periods allowed for compliance of MACT rules (in years)	3
Number of extensions allowed for installation of emission control technology	2
Number of extension periods allowed for installation of emission control technology (in years)	1
Deferral period for GHG permitting requirements for carbon dioxide emissions (in years)					3
Asset retirement obligations
Asset retirement obligation related to removal of retired generating units						12,000,000		23,000,000
Changes in the asset retirement obligation liability
Balance at the beginning of the period					48,630,000					50,871,000	48,630,000	23,746,000
Accretion expense											2,202,000	2,519,000
Liabilities incurred											256,000	11,949,000
Liabilities settled											(835,000)	(725,000)
Revisions in estimated cash flows											618,000	11,141,000
Balance at the end of the period							$ 23,746,000				$ 50,871,000	$ 48,630,000	$ 23,746,000
Collective bargaining agreement
Percentage of employees who are members of the International Brotherhood of Electrical Workers		53.00%
Non-compounded wage increase (as a percent)									3.00%	2.50%	1.75%