Retirement benefits (Details) (USD $)	3 Months Ended			6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended						12 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Pension benefits	Jun. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries Pension benefits	Jun. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Pension benefits	Jun. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries Pension benefits	Jun. 30, 2011 Pension benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2010 Pension benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2011 Pension benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2010 Pension benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Other benefits	Jun. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries Other benefits	Jun. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Other benefits	Jun. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries Other benefits	Jun. 30, 2011 Other benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2010 Other benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2011 Other benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2010 Other benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2011 Bank	Jun. 30, 2010 Bank	Jun. 30, 2011 Hawaiian Electric Industries, Inc.	Jun. 30, 2010 Hawaiian Electric Industries, Inc.	Dec. 31, 2010 Hawaiian Electric Industries, Inc.	Jun. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries	Jun. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2010 Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit 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																				$ 500,000	$ 400,000	$ 1,000,000	$ 37,000,000	$ 16,000,000	$ 31,000,000
Current estimate of contributions to defined benefit plans in current fiscal year																				2,000,000			73,000,000
Benefits expected to be paid directly by the company in current fiscal year																				1,000,000			1,000,000
Service cost		8,474,000	6,772,000	17,039,000	13,382,000	8,824,000	7,095,000	17,741,000	14,048,000	1,129,000	1,131,000	2,352,000	2,219,000	1,173,000	1,168,000	2,440,000	2,291,000
Interest cost		14,803,000	14,658,000	29,652,000	29,237,000	16,271,000	16,093,000	32,580,000	32,133,000	2,340,000	2,571,000	4,724,000	5,167,000	2,417,000	2,652,000	4,878,000	5,336,000
Expected return on plan assets		(15,352,000)	(15,353,000)	(30,636,000)	(30,677,000)	(17,172,000)	(17,221,000)	(34,273,000)	(34,415,000)	(2,618,000)	(2,728,000)	(5,226,000)	(5,443,000)	(2,657,000)	(2,766,000)	(5,305,000)	(5,518,000)
Amortization of unrecognized transition obligations								1,000	1,000	(2,000)	(2,000)	(4,000)	(4,000)
Amortization of prior service gain		(187,000)	(187,000)	(374,000)	(374,000)	(97,000)	(97,000)	(194,000)	(194,000)	(312,000)	(56,000)	(539,000)	(111,000)	(309,000)	(52,000)	(533,000)	(104,000)
Recognized actuarial loss (gain)		4,016,000	1,767,000	8,136,000	3,452,000	4,314,000	1,791,000	8,719,000	3,507,000	37,000	1,000	55,000	4,000	40,000	(2,000)	55,000	(3,000)
Net periodic benefit cost		11,754,000	7,657,000	23,817,000	15,020,000	12,140,000	7,661,000	24,574,000	15,080,000	574,000	917,000	1,362,000	1,832,000	664,000	1,000,000	1,535,000	2,002,000			20,000,000	19,000,000
Impact of PUC DandOs		(556,000)	2,020,000	(2,100,000)	5,028,000	(556,000)	2,020,000	(2,100,000)	5,028,000	1,734,000	1,333,000	2,752,000	2,621,000	1,734,000	1,333,000	2,752,000	2,621,000
Net periodic benefit cost (adjusted for impact of PUC DandOs)		11,198,000	9,677,000	21,717,000	20,048,000	11,584,000	9,681,000	22,474,000	20,108,000	2,308,000	2,250,000	4,114,000	4,453,000	2,398,000	2,333,000	4,287,000	4,623,000
Retirement benefits expense		11,754,000	7,657,000	23,817,000	15,020,000	12,140,000	7,661,000	24,574,000	15,080,000	574,000	917,000	1,362,000	1,832,000	664,000	1,000,000	1,535,000	2,002,000			20,000,000	19,000,000
Defined contribution plan
Defined contribution plan, expenses recognized																		1,700,000	1,900,000
Cash contributions by the employer to defined contribution plan																		$ 2,800,000	$ 2,800,000