Retirement benefits (Details) (USD $)	12 Months Ended											12 Months Ended		12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2011 Minimum	Dec. 31, 2011 Maximum	Dec. 31, 2011 Electric utility	Dec. 31, 2010 Electric utility	Dec. 31, 2009 Electric utility	Dec. 31, 2011 Hawaiian Electric Industries, Inc. Bank	Dec. 31, 2011 Hawaiian Electric Industries, Inc. Electric utility	Dec. 31, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Y	Dec. 31, 2010 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2007 Hawaii Electric Light Company, Inc. (HELCO) Y	Dec. 31, 2011 Hawaii Electric Light Company, Inc. (HELCO)	Dec. 31, 2011 Pension benefits	Dec. 31, 2010 Pension benefits	Dec. 31, 2009 Pension benefits	Dec. 31, 2011 Other benefits	Dec. 31, 2010 Other benefits	Dec. 31, 2009 Other benefits
Retirement benefits
Vested percentage of interest of each affected participant after participating employer terminates participation								100.00%
Number of years for which regulatory asset/liability for each utility will be amortized, beginning with respective utility's next rate case	5											5
Executive life and nonqualified pension plan expenses	$ 1,600,000
Regulatory asset charges pretax	165,000,000	55,000,000
Regulatory assets										649,106,000	470,981,000		12,800,000
Regulatory assets recovery period (in years)										5
Remaining prepaid pension assets										3,000,000
Retirement benefits expense					34,000,000	39,000,000	32,000,000
Employer's additional matching contribution on the first 6 percent of employee deferrals (as a percent)					50.00%				50.00%
Maximum percentage of participant deferrals eligible for Employer contribution match, towards defined contribution plan (as a percent)					6.00%				6.00%
Changes in benefit obligation
Benefit obligation, balance at the beginning of the period														1,174,534,000	1,014,287,000		180,332,000	170,572,000
Service cost														35,016,000	28,801,000	25,688,000	4,409,000	4,739,000	4,846,000
Interest cost														64,966,000	64,527,000	61,988,000	9,534,000	10,378,000	10,981,000
Amendments																	(11,365,000)	(7,713,000)
Actuarial losses														104,970,000	121,898,000		16,518,000	11,817,000
Benefits paid and expenses														(57,056,000)	(54,979,000)		(8,879,000)	(9,461,000)
Benefit obligation, balance at the end of the period														1,322,430,000	1,174,534,000	1,014,287,000	190,549,000	180,332,000	170,572,000
Changes in fair value of plan assets
Fair value of plan assets, balance at the beginning of the period														832,356,000	738,971,000		151,117,000	134,608,000
Actual return (loss) on plan assets														(9,713,000)	119,446,000		(2,308,000)	21,271,000
Employer contribution														72,931,000	27,803,000		2,030,000	3,989,000
Benefits paid and expenses														(55,994,000)	(53,864,000)		(7,847,000)	(8,751,000)
Fair value of plan assets, balance at the end of the period														839,580,000	832,356,000	738,971,000	142,992,000	151,117,000	134,608,000
Accrued benefit liability, balance at the end of the period														(482,850,000)	(342,178,000)		(47,557,000)	(29,215,000)
Changes in accumulated other comprehensive income
AOCI, balance at beginning of the period (excluding impact of PUC D&Os)														366,552,000	302,147,000		9,036,000	14,693,000
Recognized during year - net recognized transition obligation														(2,000)	(2,000)
Recognized during year - prior service credit														389,000	388,000		1,494,000	396,000
Recognized during year - net actuarial gains (losses)														(16,987,000)	(7,392,000)		(234,000)	14,000
Occurring during year - prior service cost																	(11,365,000)	(7,714,000)
Occurring during year - net actuarial losses														183,585,000	71,411,000		29,753,000	1,647,000
AOCI, balance at end of the period (excluding impact of PUC D&Os)														533,537,000	366,552,000	302,147,000	28,684,000	9,036,000	14,693,000
Cumulative impact of PUC D&Os														(486,710,000)	(340,187,000)		(29,183,000)	(10,880,000)
AOCI, balance at end of the period														46,827,000	26,365,000		(499,000)	(1,844,000)
Net actuarial loss														534,054,000	367,456,000		48,152,000	18,633,000
Prior service gain														(518,000)	(907,000)		(19,468,000)	(9,597,000)
Net transition obligation														1,000	3,000
Income taxes														(18,495,000)	(10,403,000)		194,000	717,000
AOCI, net of taxes,(benefits) balance at the end of the period														28,332,000	15,962,000		(305,000)	(1,127,000)
Defined benefit pension plans with accumulated benefit obligations in excess of plan assets
Aggregate accumulated benefit obligations														1,182,000,000	990,000,000
Plan assets														840,000,000	758,000,000
Single sum distribution option														50,000
Percentage of accelerated distribution which can be elected														50.00%
Company's current estimate of contributions in next fiscal year	107,000,000													104,000,000			69,000,000
Funded status of the plan (as a percent)														80.00%
Expected cash funding for qualified defined benefit plans
2012	107,000,000													104,000,000			69,000,000
2013														89,000,000			72,000,000
2014																	75,000,000
2015																	78,000,000
2016																	82,000,000
2017 through 2020																	$ 469,000,000
Fair value of plan assets, valuation difference amortized in first year (as a percent)	0.00%
Fair value of plan assets, valuation difference amortized in two to five years (as a percent)	25.00%
Number of past years for adding or subtracting the unamortized differences from fair value	4
Percentage of range around fair value	15.00%
Threshold percentage around fair value			85.00%	115.00%