Retirement benefits (Details) (USD $)	6 Months Ended	9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended					9 Months Ended
	Sep. 30, 2011	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Pension benefits	Sep. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries Pension benefits	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Pension benefits	Sep. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries Pension benefits	Sep. 30, 2011 Pension benefits Hawaiian Electric Industries, Inc.	Sep. 30, 2010 Pension benefits Hawaiian Electric Industries, Inc.	Sep. 30, 2011 Pension benefits Hawaiian Electric Industries, Inc.	Sep. 30, 2010 Pension benefits Hawaiian Electric Industries, Inc.	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Other benefits	Sep. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries Other benefits	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Other benefits	Sep. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries Other benefits	Sep. 30, 2011 Other benefits Hawaiian Electric Industries, Inc.	Sep. 30, 2010 Other benefits Hawaiian Electric Industries, Inc.	Sep. 30, 2011 Other benefits Hawaiian Electric Industries, Inc.	Sep. 30, 2010 Other benefits Hawaiian Electric Industries, Inc.	Sep. 30, 2011 Hawaiian Electric Industries, Inc.	Sep. 30, 2010 Hawaiian Electric Industries, Inc.	Dec. 31, 2010 Hawaiian Electric Industries, Inc.	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2010 Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit pension and other postretirement plans
Employer's additional matching contribution on the first 6 percent of employee deferrals (as a percent)	50.00%
Maximum percentage of participant deferrals eligible for Employer contribution match, towards defined contribution plan (as a percent)	6.00%
Contributions made to defined benefit plans																				$ 1,200,000	$ 600,000		$ 55,000,000	$ 24,000,000
Current estimate of contributions to defined benefit plans in current fiscal year																				2,000,000		1,000,000	73,000,000		31,000,000
Benefits expected to be paid directly by the company in current fiscal year																				1,000,000			1,000,000
Service cost				8,182,000	7,097,000	25,221,000	20,479,000	8,525,000	7,376,000	26,266,000	21,424,000	827,000	1,206,000	3,179,000	3,425,000	868,000	1,248,000	3,308,000	3,539,000
Interest cost				14,656,000	14,816,000	44,308,000	44,053,000	16,137,000	16,197,000	48,717,000	48,330,000	2,197,000	2,500,000	6,921,000	7,667,000	2,273,000	2,565,000	7,151,000	7,901,000
Expected return on plan assets				(15,574,000)	(15,408,000)	(46,210,000)	(46,085,000)	(17,400,000)	(17,272,000)	(51,673,000)	(51,687,000)	(2,655,000)	(2,759,000)	(7,881,000)	(8,202,000)	(2,687,000)	(2,792,000)	(7,992,000)	(8,310,000)
Amortization of unrecognized transition obligation								1,000	1,000	2,000	2,000	(2,000)	(2,000)	(6,000)	(6,000)
Amortization of prior service gain				(187,000)	(186,000)	(561,000)	(560,000)	(98,000)	(97,000)	(292,000)	(291,000)	(590,000)	(86,000)	(1,129,000)	(197,000)	(587,000)	(83,000)	(1,120,000)	(187,000)
Recognized actuarial loss (gain)								4,005,000	1,942,000	12,724,000	5,449,000					115,000	(5,000)	170,000	(8,000)
Net periodic benefit cost				10,756,000	8,244,000	34,573,000	23,264,000	11,170,000	8,147,000	35,744,000	23,227,000	(119,000)	857,000	1,243,000	2,689,000	(18,000)	933,000	1,517,000	2,935,000
Impact of PUC DandOs				(713,000)	2,574,000	(2,813,000)	7,602,000	(713,000)	2,574,000	(2,813,000)	7,602,000	327,000	1,512,000	3,079,000	4,133,000	327,000	1,512,000	3,079,000	4,133,000
Net periodic benefit cost (adjusted for impact of PUC DandOs)				10,043,000	10,818,000	31,760,000	30,866,000	10,457,000	10,721,000	32,931,000	30,829,000	208,000	2,369,000	4,322,000	6,822,000	309,000	2,445,000	4,596,000	7,068,000
Retirement benefits expense																				28,000,000	29,000,000		27,000,000	29,000,000
Defined contribution plan
Defined contribution plan, expenses recognized		2,600,000	2,900,000
Cash contributions by the employer to defined contribution plan		$ 3,200,000	$ 3,200,000