Retirement benefits (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Defined benefit plans
Contributions made to defined benefit plans	$ 0
Current estimate of contributions to defined benefit plans in current fiscal year	86,000,000		78,000,000
Benefits expected to be paid directly by the company in current fiscal year	2,000,000		1,000,000
Retirement benefits expense	11,000,000	8,000,000
Number of years for which regulatory asset/liability for each utility will be amortized, beginning with respective utility's next rate case	5 years
Defined contribution plan, expenses recognized	1,000,000	900,000
Cash contributions by the employer to defined contribution plan	2,400,000	2,200,000
American Savings Bank (ASB)
Defined benefit plans
Current estimate of contributions to defined benefit plans in current fiscal year	0		13,000,000
Hawaiian Electric Industries, Inc.
Defined benefit plans
Contributions made to defined benefit plans			1,000,000
Current estimate of contributions to defined benefit plans in current fiscal year	2,000,000		2,000,000
Benefits expected to be paid directly by the company in current fiscal year	1,000,000
Electric utility
Defined benefit plans
Contributions made to defined benefit plans	21,000,000	27,000,000
Current estimate of contributions to defined benefit plans in current fiscal year	84,000,000		63,000,000
Benefits expected to be paid directly by the company in current fiscal year	1,000,000
Pension benefits
Defined benefit plans
Funded status of the plan (as a percent)	80.00%
Service cost	14,089,000	10,191,000
Interest cost	16,106,000	16,771,000
Expected return on plan assets	(18,085,000)	(17,856,000)
Amortization of prior service gain	(24,000)	(81,000)
Amortization of net actuarial loss	9,819,000	6,423,000
Net periodic benefit cost	21,905,000	15,448,000
Impact of PUC D&Os	(7,436,000)	(3,857,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	14,469,000	11,591,000
Other benefits
Defined benefit plans
Service cost	1,049,000	1,096,000
Interest cost	1,931,000	2,281,000
Expected return on plan assets	(2,562,000)	(2,621,000)
Amortization of prior service gain	(448,000)	(448,000)
Amortization of net actuarial loss	521,000	453,000
Net periodic benefit cost	491,000	761,000
Impact of PUC D&Os	(397,000)	(680,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	$ 94,000	$ 81,000