Retirement benefits (Details) (USD $)	9 Months Ended		12 Months Ended			9 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 American Savings Bank (ASB)	Dec. 31, 2012 American Savings Bank (ASB)	Sep. 30, 2013 Hawaiian Electric Industries, Inc.	Dec. 31, 2012 Hawaiian Electric Industries, Inc.	Sep. 30, 2013 Electric utility	Sep. 30, 2012 Electric utility	Dec. 31, 2012 Electric utility	Sep. 30, 2013 Pension benefits	Sep. 30, 2012 Pension benefits	Sep. 30, 2013 Pension benefits	Sep. 30, 2012 Pension benefits	Sep. 30, 2013 Other benefits	Sep. 30, 2012 Other benefits	Sep. 30, 2013 Other benefits	Sep. 30, 2012 Other benefits
Defined benefit plans
Contributions made to defined benefit plans								$ 62,000,000	$ 64,000,000
Current estimate of contributions to defined benefit plans in current fiscal year	83,000,000		78,000,000	0	13,000,000	2,000,000	2,000,000	81,000,000		63,000,000
Benefits expected to be paid directly by the company in current fiscal year	2,000,000		1,000,000			1,000,000		1,000,000
Service cost											14,097,000	10,816,000	42,307,000	32,404,000	1,077,000	1,054,000	3,229,000	3,158,000
Interest cost											16,187,000	16,868,000	48,600,000	50,612,000	1,891,000	2,252,000	5,677,000	6,756,000
Expected return on plan assets											(18,134,000)	(17,796,000)	(54,401,000)	(53,388,000)	(2,531,000)	(2,579,000)	(7,614,000)	(7,757,000)
Amortization of net transition obligation											0	1,000	0	1,000	0	0	0	0
Amortization of prior service gain											(24,000)	(81,000)	(73,000)	(244,000)	(448,000)	(448,000)	(1,345,000)	(1,345,000)
Amortization of net actuarial loss											9,560,000	6,425,000	28,878,000	19,251,000	398,000	373,000	1,203,000	1,125,000
Net periodic benefit cost											21,686,000	16,233,000	65,311,000	48,636,000	387,000	652,000	1,150,000	1,937,000
Impact of PUC D&Os											(9,257,000)	(3,460,000)	(28,847,000)	(12,294,000)	(332,000)	(552,000)	(1,018,000)	(1,648,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)											12,429,000	12,773,000	36,464,000	36,342,000	55,000	100,000	132,000	289,000
Retirement benefits expense	24,000,000	27,000,000
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	3,100,000	2,700,000
Cash contributions by the employer to defined contribution plan	$ 3,700,000	$ 3,200,000