Retirement benefits (Details) (USD $)	6 Months Ended				6 Months Ended			6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Apr. 02, 2011	Jun. 30, 2012 Hawaiian Electric Industries, Inc.	Jun. 30, 2011 Hawaiian Electric Industries, Inc.	Dec. 31, 2011 Hawaiian Electric Industries, Inc.	Jun. 30, 2012 Electric utility	Jun. 30, 2011 Electric utility	Dec. 31, 2011 Electric utility	Jun. 30, 2012 Pension benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2011 Pension benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2012 Pension benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2011 Pension benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2012 Other benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2011 Other benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2012 Other benefits Hawaiian Electric Industries, Inc.	Jun. 30, 2011 Other benefits Hawaiian Electric Industries, Inc.
Defined benefit plans
Contributions made to defined benefit plans	$ 53,000,000	$ 38,000,000			$ 1,000,000			$ 52,000,000	$ 38,000,000
Current estimate of contributions to defined benefit plans in current fiscal year	107,000,000		75,000,000		3,000,000		2,000,000	104,000,000		73,000,000
Benefits expected to be paid directly by the company in current fiscal year	2,000,000				1,000,000			1,000,000
Service cost											11,397,000	8,824,000	21,588,000	17,741,000	1,008,000	1,173,000	2,104,000	2,440,000
Interest cost											16,973,000	16,271,000	33,744,000	32,580,000	2,223,000	2,417,000	4,504,000	4,878,000
Expected return on plan assets											(17,736,000)	(17,172,000)	(35,592,000)	(34,273,000)	(2,557,000)	(2,657,000)	(5,178,000)	(5,305,000)
Amortization of net transition obligation														1,000
Amortization of prior service gain											(82,000)	(97,000)	(163,000)	(194,000)	(449,000)	(309,000)	(897,000)	(533,000)
Amortization of net actuarial loss											6,403,000	4,314,000	12,826,000	8,719,000	299,000	40,000	752,000	55,000
Net periodic benefit cost											16,955,000	12,140,000	32,403,000	24,574,000	524,000	664,000	1,285,000	1,535,000
Impact of PUC D&Os											(4,977,000)	(556,000)	(8,834,000)	(2,100,000)	(416,000)	1,734,000	(1,096,000)	2,752,000
Net periodic benefit cost (adjusted for impact of PUC D&Os)											11,978,000	11,584,000	23,569,000	22,474,000	108,000	2,398,000	189,000	4,287,000
Amount available as single sum distribution option under accelerated distribution options				50,000
Funded status of retirement plan (as a percent)				80.00%
Percentage of participant's total benefit that may be elected while partial restrictions are in effect				50.00%
Retirement benefits expense					17,000,000	20,000,000
Defined contribution plan, expenses recognized	1,800,000	1,700,000
Cash contributions by the employer to defined contribution plan	$ 2,700,000	$ 2,800,000